Q:

Approving overly substantial edits to answers

I'm in the habit of rejecting edits to answers that add a substantial amount of information that the original answerer clearly didn't just forget to add in but didn't plan on adding to begin with.
Here's an example of a case like this.
The answer was posted 3 hours prior to the edit being made. The edit in question added what looks to be significant (and necessary) information to the answer.
I rejected that edit because the mistake of leaving that bit out is the answerer's to make and not our's to fix.
So, how exactly should I deal with those kinds of edits? Is it usually just up to the reviewer to approve or reject it? I can see a reason to approve it being that other changes were also made.
For further reference, here is another example. Here, the lack of including "my" before "toolbar" in the code and the capitalization of "Bar" in "UIToolbar" may or may not have been a mistake that the answerer simply overlooked, but I still think it's their responsibility to fix it. If their answer is incorrect, they should take responsibility.

A:

Well, I for one don't want half answers, or answers where some vital bit is missing.  There's no guarantee the person that answered the question will ever come back to their answer to make changes.
I'm all for editing the answer and making it (and thus the whole site) more useful.  That is, after all, the whole point of allowing people to edit.
If that were the only change made, it's worthwhile.
I'm actually rather dismayed to hear you've been doing this, as it makes me wonder how many great answers have been left as mediocre answers after someone took the time and effort to better it, just because you would rather point a finger and say "you screwed up, you should fix it" to the original poster.  
It doesn't matter in the least who "fixes" (for lack of a better term) it, it should be fixed if it needs to be.

A:

The first example requires knowledge of the subject matter to decide. If you don't have this subject knowledge, skip it (“Not sure”). If it is true that the permission is required, then this is an important complementary piece of information. This extra information doesn't belong in an answer of its own. It could be posted as a comment, but that would make legible formatting impossible and would make it less visible: it's better to have it in the answer.
The second example is definitely a good edit. It fixes syntax errors in the original post and doesn't change the intended meaning in any way. It's obvious that this is something the original answerer did plan to write, only he typed this code without the benefit of a compiler to point out the typos.
As the FAQ says:

If you see something that needs improvement, click edit and help us make it so! (…) If you are not comfortable with the idea of your contributions being collaboratively edited by other trusted users, this may not be the site for you.

Adding relevant complements or fixing minor mistakes in an answer is good. Stack Exchange aims at being a repository of good answers, not a repository of incomplete and only-mostly-correct answers. It isn't just the answerer's responsibility to fix mistakes, it's the whole community's.

