user10844: Answering questions here in buddhism.stackexchange.com is often Dhamma teaching, or at least an effort of it. How can that be rightly done?

user19354: Good kindly question; Sharing The Dharma correctly, appropriately, kindly, compassionately, sincerely, openly, forthrightly, unattachedly, generously, & nicely etc, is 'good'!!!

user2282: 
Answering questions here in buddhism.stackexchange.com is often Dhamma teaching, or at least an effort of it. How can that be rightly done?

Not necessary. It's Dhamma "teaching" only if one's confident that s/he's gained mastery of the Dhamma both in theory and in practice. Short of any of those factors and it's more like Dhamma "sharing", where one shares suttas/comys. references and any related backup literatures in the hope that they can address the inquiry raised by the OP. And so, by sharing, just providing personal opinion is simply not sufficient. Always follow up with supporting evidence from the suttas/comys/related literatures, etc.

user10844: From Udayi Sutta (AN5.159):

"It's not easy to teach the Dhamma to others, Ananda. The Dhamma
should be taught to others only when five qualities are established
within the person teaching. Which five?
"[1] The Dhamma should be taught with the thought, 'I will speak
step-by-step.'
"[2] The Dhamma should be taught with the thought, 'I will speak
explaining the sequence [of cause & effect].'
"[3] The Dhamma should be taught with the thought, 'I will speak out
of compassion.'
"[4] The Dhamma should be taught with the thought, 'I will speak not
for the purpose of material reward.'
"[5] The Dhamma should be taught with the thought, 'I will speak
without hurting myself or others.'
"It's not easy to teach the Dhamma to others, Ananda. The Dhamma
should be taught to others only when these five qualities are
established within the person teaching."

Source: http://www.accesstoinsight.org/tipitaka/an/an05/an05.159.than.html
I want to highlight this sutta to everyone who wants to teach Dhamma/Dharma here or elsewhere.
Some comments:
[1] Aj Thanissaro's "step-by-step" is translate from ānupubbī, meaning "gradually". This means we should not teach what is beyond the ability of the listener. This implies that we should first understand the listener's situation.
[2] I'm not sure why he translates pariyāyadassāvī as "explaining the sequence". Although pariyāya can mean "sequence", translating it this way makes this point a repetition of the first. Pariyāya has a range of meanings, and in this context I think it means "way" or "habit", as in "mental way/habit" (cetopariyāya). Thus, as a whole, pariyāyadassāvī is "(as) one who sees of the (mental) habit". In modern terms, this point means we need to understand human psychology.
[3] This point should be plain enough, but let me point out that "compassion" is not translated from karuṇā but from anuddayata, which I prefer to translate as "kindness".
[4] "For the purpose of material reward" is somewhat loosely translated from āmisantaro but I'm happy enough with it. Although in SE you wouldn't get any physical reward, the reputation points and badges are enough to be considered "material" (as opposed to "spiritual"). Are you greedy for that?
[5] The last point suggest that we should check what we're actually doing as we try to teach. "Hurting" in general means decreasing our good qualities, increasing the defilements, strengthening the ego, thus ultimately increasing suffering. So, in the name of "teaching Dhamma", are we hurting ourselves? Or hurting others? Instead of helping them, are we causing them to be greedier, feel small, or in any other way increase their defilements and suffering?
Please reflect on this.

user471: I think most of the people contributing on Buddhism.SE do not qualify to call themselves Dhamma teachers. Their answers also cannot be considered a Dhamma teaching.
The following is a better approximation, from Mahāgosiṅga Sutta (MN 32):

“Reverend Sāriputta, it’s when two mendicants engage in discussion
about the teaching. They question each other and answer each other’s
questions without faltering, and their discussion on the teaching
flows on. That’s the kind of mendicant who would beautify this park.”


As a side note - a question arose in the comments whether the MN 32 quote should be translated as "about the teaching / Dhamma" (Sujato translation) or "on the higher Dhamma (Abhidhamma)" (Bodhi translation).
The following opinion by Bhikkhu Analayo supports the Sujato translation.
From pages 70 - 71 of the book "The Dawn of Abhidharma" by Bhikkhu Analayo:

In the Mahāgosiṅga-sutta and its Madhyama-āgama parallel the reference to “abhidharma  talk”  or  to  discussing  the “abhidharma”
occurs alongside “Dharma talk” or “teaching the Dharma”. This gives
the impression that the two terms Dharma and abhidharma are here
interchangeable. In the Mahāgosiṅga-sutta,  the  prefix abhi- would
thus  convey the  sense  of “about”  or “concerning” the Dharma. The
passage  would then describe having a talk “about the Dharma” and
discussing “about the Dharma”, abhidharma.49
The notion that the prefix abhi- conveys a sense of superiority appears to reflect a later understanding of the implications of the
term. In line with later understanding, the commentary on the
Dhammasaṅgaṇī, the Atthasālinī, refers to the present passage in
support of the authenticity of the Abhidharma-piṭaka as the Buddha’s
word.50
A discourse in the Aṅguttara-nikāya describes a group of elder monks seated together “talking abhidharma talk”.51 In this
case the Madhyama-āgama parallel does not employ the term abhidharma
at all, but rather describes that these monks were “wanting to settle
a matter of dispute, namely  to  discuss  what  is  Dharma  and
Vinaya,  what is the  Buddha’s teaching”.52 This case would
be in line with the impression that abhidharma talk can simply stand
for talk about the Dharma.


10844: <p>Answering questions here in <code>buddhism.stackexchange.com</code> is often Dhamma teaching, or at least an effort of it. How can that be rightly done?</p>
 19354: <p>Good kindly question; Sharing The Dharma correctly, appropriately, kindly, compassionately, sincerely, openly, forthrightly, unattachedly, generously, &amp; nicely etc, is 'good'!!!</p>
 2282: <blockquote>
<p>Answering questions here in buddhism.stackexchange.com is often Dhamma teaching, or at least an effort of it. How can that be rightly done?</p>
</blockquote>
<p>Not necessary. It's Dhamma &quot;teaching&quot; only if one's confident that s/he's gained mastery of the Dhamma both in theory and in practice. Short of any of those factors and it's more like Dhamma &quot;sharing&quot;, where one shares suttas/comys. references and any related backup literatures in the hope that they can address the inquiry raised by the OP. And so, by sharing, just providing personal opinion is simply not sufficient. Always follow up with supporting evidence from the suttas/comys/related literatures, etc.</p>
 10844: <p>From Udayi Sutta (AN5.159):</p>
<blockquote>
<p>&quot;It's not easy to teach the Dhamma to others, Ananda. The Dhamma
should be taught to others only when five qualities are established
within the person teaching. Which five?</p>
<p>&quot;[1] The Dhamma should be taught with the thought, 'I will speak
step-by-step.'</p>
<p>&quot;[2] The Dhamma should be taught with the thought, 'I will speak
explaining the sequence [of cause &amp; effect].'</p>
<p>&quot;[3] The Dhamma should be taught with the thought, 'I will speak out
of compassion.'</p>
<p>&quot;[4] The Dhamma should be taught with the thought, 'I will speak not
for the purpose of material reward.'</p>
<p>&quot;[5] The Dhamma should be taught with the thought, 'I will speak
without hurting myself or others.'</p>
<p>&quot;It's not easy to teach the Dhamma to others, Ananda. The Dhamma
should be taught to others only when these five qualities are
established within the person teaching.&quot;</p>
</blockquote>
<p>Source: <a href="http://www.accesstoinsight.org/tipitaka/an/an05/an05.159.than.html" rel="nofollow noreferrer">http://www.accesstoinsight.org/tipitaka/an/an05/an05.159.than.html</a></p>
<p>I want to highlight this sutta to everyone who wants to teach Dhamma/Dharma here or elsewhere.</p>
<p>Some comments:</p>
<p>[1] Aj Thanissaro's &quot;step-by-step&quot; is translate from <em>ānupubbī</em>, meaning &quot;gradually&quot;. This means we should not teach what is beyond the ability of the listener. This implies that we should <em><strong>first</strong></em> understand the listener's situation.</p>
<p>[2] I'm not sure why he translates <em>pariyāyadassāvī</em> as &quot;explaining the sequence&quot;. Although <em>pariyāya</em> can mean &quot;sequence&quot;, translating it this way makes this point a repetition of the first. <em>Pariyāya</em> has a range of meanings, and in this context I think it means &quot;way&quot; or &quot;habit&quot;, as in &quot;mental way/habit&quot; (<em>cetopariyāya</em>). Thus, as a whole, <em>pariyāyadassāvī</em> is &quot;(as) one who sees of the (mental) habit&quot;. In modern terms, this point means we need to understand human psychology.</p>
<p>[3] This point should be plain enough, but let me point out that &quot;compassion&quot; is not translated from <em>karuṇā</em> but from <em>anuddayata</em>, which I prefer to translate as &quot;kindness&quot;.</p>
<p>[4] &quot;For the purpose of material reward&quot; is somewhat loosely translated from <em>āmisantaro</em> but I'm happy enough with it. Although in SE you wouldn't get any physical reward, the reputation points and badges are enough to be considered &quot;material&quot; (as opposed to &quot;spiritual&quot;). Are you greedy for that?</p>
<p>[5] The last point suggest that we should check what we're actually doing as we try to teach. &quot;Hurting&quot; in general means decreasing our good qualities, increasing the defilements, strengthening the ego, thus ultimately increasing suffering. So, in the name of &quot;teaching Dhamma&quot;, are we hurting ourselves? Or hurting others? Instead of helping them, are we causing them to be greedier, feel small, or in any other way increase their defilements and suffering?</p>
<p>Please reflect on this.</p>
 471: <p>I think most of the people contributing on Buddhism.SE do not qualify to call themselves Dhamma teachers. Their answers also cannot be considered a Dhamma teaching.</p>
<p>The following is a better approximation, from Mahāgosiṅga Sutta (<a href="https://suttacentral.net/mn32/en/sujato" rel="nofollow noreferrer">MN 32</a>):</p>
<blockquote>
<p>“Reverend Sāriputta, it’s when two mendicants engage in discussion
about the teaching. They question each other and answer each other’s
questions without faltering, and their discussion on the teaching
flows on. That’s the kind of mendicant who would beautify this park.”</p>
</blockquote>
<hr />
<p>As a side note - a question arose in the comments whether the MN 32 quote should be translated as &quot;about the teaching / Dhamma&quot; (Sujato translation) or &quot;on the higher Dhamma (Abhidhamma)&quot; (Bodhi translation).</p>
<p>The following opinion by Bhikkhu Analayo supports the Sujato translation.</p>
<p>From pages 70 - 71 of the book &quot;<a href="https://www.buddhismuskunde.uni-hamburg.de/pdf/5-personen/analayo/dawn-abhidharma.pdf" rel="nofollow noreferrer">The Dawn of Abhidharma</a>&quot; by Bhikkhu Analayo:</p>
<blockquote>
<p>In the Mahāgosiṅga-sutta and its Madhyama-āgama parallel the reference to “abhidharma  talk”  or  to  discussing  the “abhidharma”
occurs alongside “Dharma talk” or “teaching the Dharma”. This gives
the impression that the two terms Dharma and abhidharma are here
interchangeable. In the Mahāgosiṅga-sutta,  the  prefix abhi- would
thus  convey the  sense  of “about”  or “concerning” the Dharma. The
passage  would then describe having a talk “about the Dharma” and
discussing “about the Dharma”, abhidharma.<sup>49</sup></p>
<p>The notion that the prefix abhi- conveys a sense of superiority appears to reflect a later understanding of the implications of the
term. In line with later understanding, the commentary on the
Dhammasaṅgaṇī, the Atthasālinī, refers to the present passage in
support of the authenticity of the Abhidharma-piṭaka as the Buddha’s
word.<sup>50</sup></p>
<p>A discourse in the Aṅguttara-nikāya describes a group of elder monks seated together “talking abhidharma talk”.<sup>51</sup> In this
case the Madhyama-āgama parallel does not employ the term abhidharma
at all, but rather describes that these monks were “wanting to settle
a matter of dispute, namely  to  discuss  what  is  Dharma  and
Vinaya,  what is the  Buddha’s teaching”.<sup>52</sup> This case would
be in line with the impression that abhidharma talk can simply stand
for talk about the Dharma.</p>
</blockquote>
