What to do with edits that add new content to an existing question/answer?

Question

I try to review edits as good as I can. Mostly these are corrections in spelling or formatting changes, which is fine. But now I just encountered an edit where another user added completely new content to an existing answer.

I'm not able to judge if this new content is really useful or accurate (it could even result in downvotes of the answer if the new content is bogus). How should edits that add new content to an answer be handled? Should I just approve it and let the OP rollback if he desires? How do the mods handle edits like this?

Answer 1

I usually stick to approving edits that make changes to and improve formatting, spelling errors, and grammar.

If an edit is adding significant new content that was not present in an existing answer I most often would deny it and suggest that (if they want to provide context or something) they do it in the comments or by posting their own answer.

Answer 2

An explanation of what should and shouldn't be edited can be found here.

Quick summary (not exhaustive list)

Allowed:
- Spelling/grammar improvements
- Embedding an already-linked image into the post
- Moving relevant, meaningful content from comments on the post into the post

Not Allowed:
- Adding a comment to the post (ex "I have this problem too!")
- Adding, deleting, or changing anything that might change the intended meaning of the post
- Trivial things like changing British English spellings to American English

Basically, if it is a meaningful improvement that doesn't change the intended meaning (or what the intended meaning of the post will be understood to be), it should be accepted.

Meaningless edits or edits that change the meaning of the post should be rejected.

In cases where it's not clear whether the meaning may be changed, I'd err on the side of caution - don't approve the edit if it might cause someone to read the post as meaning something different than what it would mean without the edit.