user8157: I read the following comment on the internet (reference):

By existing you are attached to this reality. If I die then I won't exist according to Buddhism. Therefore I won't be attached to reality.
  How then does killing yourself not free yourself from attachment? How
  can I possibly be attached to reality if I am dead? How was the Buddha
  free from attachment if he wrote a book and made a religion? That
  means that he was attached to reality. You can only be not attached to
  reality if you don't exist.

Is the existence of life a form of attachment?
Is the teaching of the Dhamma (of non-attachment) a form of attachment?

user11541: 
If I die then I won't exist according to Buddhism.

The above statement is wrong. Whether Tathagata exists or not after death or Nirvana is not declared by Buddha. 
Is the existence of life a form of attachment?
Existence of life is conditional. One of the conditions is attachment. Therefore it is wrong to say that existence of life is form of condition. It doesnt make sense. For example seed is the condition for the existence of plant but water and earth are conditions for its existence and growth. It doesnt mean that seed is a form of earth or water. 
Is the teaching of the Dhamma (of non-attachment) a form of attachment?
Teaching of Dhamma is a form of attachment which encourages you to be unattached to any kind of Dhamma. Teaching of Dhamma is a wholesome attachment. Teaching of Dhamma is like a medicine which is necessary for the sick.  

user-1: 
By existing you are attached to this reality. 

There are many logical fallacies in this comment. By existing, you are not attached to this reality, the reality of existence precedes your being here, you get emerged into this reality of existence, so you are simply here, not as an attachment but as a part of that very existence. 

If I die then I won't exist according to Buddhism. 

This is also wrong if you die according to Buddhism you will be reborn.

How then does killing yourself not free yourself from attachment?

Killing your self you are getting reborn in lower realms and nothing to do with attachment. The attachment might come later in that lower rebirth which will further the suffering. 

How can I possibly be attached to reality if I am dead?

You were not attached to 'reality' even when you were alive, you were attached to things which were giving you pleasure.

How was the Buddha free from attachment if he wrote a book and made
  a religion?

He didn't.

That means that he was attached to reality. You can only be not attached to reality if you don't exist.

The only way you not exist is through Nibbana. 
Following answers are for an instructed questioner.
Is the existence of life a form of attachment?
The existence of life is not a form of attachment, but as long as you are alive you can be attached to life. Mere existence is not an attachment. Attachment is a potential, it's not a manifestation of sheer existence. You get attached, the attachment is not a part of five aggregates. Attachment does not make a life. 
Is the teaching of the Dhamma (of non-attachment) a form of attachment?
The teaching of Dhamma is not a form of attachment but there is a real possibility that you can get attached to becoming a teacher by developing an ego of a teacher. Again it lies as a potential. 

8157: <p>I read the following comment on the internet (<a href="https://chat.stackexchange.com/rooms/82510/discussion-on-answer-by-dhammadhatu-if-buddhists-believe-that-life-is-just-suffe">reference</a>):</p>

<blockquote>
  <p><em>By existing you are attached to this reality. If I die then I won't exist according to Buddhism. Therefore I won't be attached to reality.
  How then does killing yourself not free yourself from attachment? How
  can I possibly be attached to reality if I am dead? How was the Buddha
  free from attachment if he wrote a book and made a religion? That
  means that he was attached to reality. You can only be not attached to
  reality if you don't exist.</em></p>
</blockquote>

<p>Is the existence of life a form of attachment?</p>

<p>Is the teaching of the Dhamma (of non-attachment) a form of attachment?</p>
 11541: <blockquote>
  <p>If I die then I won't exist according to Buddhism.</p>
</blockquote>

<p>The above statement is wrong. Whether Tathagata exists or not after death or Nirvana is not declared by Buddha. </p>

<p><strong>Is the existence of life a form of attachment?</strong></p>

<p>Existence of life is conditional. One of the conditions is attachment. Therefore it is wrong to say that existence of life is form of condition. It doesnt make sense. For example seed is the condition for the existence of plant but water and earth are conditions for its existence and growth. It doesnt mean that seed is a form of earth or water. </p>

<p><strong>Is the teaching of the Dhamma (of non-attachment) a form of attachment?</strong></p>

<p>Teaching of Dhamma is a form of attachment which encourages you to be unattached to any kind of Dhamma. Teaching of Dhamma is a wholesome attachment. Teaching of Dhamma is like a medicine which is necessary for the sick.  </p>
 -1: <blockquote>
  <p><em>By existing you are attached to this reality.</em> </p>
</blockquote>

<p>There are many logical fallacies in this comment. By existing, you are not attached to this reality, the reality of existence precedes your being here, you get emerged into this reality of existence, so you are simply here, not as an attachment but as a part of that very existence. </p>

<blockquote>
  <p><em>If I die then I won't exist according to Buddhism.</em> </p>
</blockquote>

<p>This is also wrong if you die according to Buddhism you will be reborn.</p>

<blockquote>
  <p><em>How then does killing yourself not free yourself from attachment?</em></p>
</blockquote>

<p>Killing your self you are getting reborn in lower realms and nothing to do with attachment. The attachment might come later in that lower rebirth which will further the suffering. </p>

<blockquote>
  <p><em>How can I possibly be attached to reality if I am dead?</em></p>
</blockquote>

<p>You were not attached to 'reality' even when you were alive, you were attached to things which were giving you pleasure.</p>

<blockquote>
  <p><em>How was the Buddha free from attachment if he wrote a book and made
  a religion?</em></p>
</blockquote>

<p>He didn't.</p>

<blockquote>
  <p><em>That means that he was attached to reality. You can only be not attached to reality if you don't exist.</em></p>
</blockquote>

<p>The only way you not exist is through Nibbana. </p>

<p>Following answers are for an instructed questioner.</p>

<p><strong>Is the existence of life a form of attachment?</strong></p>

<p>The existence of life is not a form of attachment, but as long as you are alive you can be attached to life. Mere existence is not an attachment. Attachment is a potential, it's not a manifestation of sheer existence. You get attached, the attachment is not a part of five aggregates. Attachment does not make a life. </p>

<p><strong>Is the teaching of the Dhamma (of non-attachment) a form of attachment?</strong></p>

<p>The teaching of Dhamma is not a form of attachment but there is a real possibility that you can get attached to becoming a teacher by developing an ego of a teacher. Again it lies as a potential. </p>
