I was one of the two people who rejected that edit. My reasons for rejecting were twofold:
- The edit inserted the phrase
**Update** which jumped out and immediately triggered an alarm bell - Stack Overflow isn't a forum and answers are expected to be more like a wiki page or a knowledge base than a form thread, text like that makes answers look a little too much like forum posts for comfort in my view.
- The edit was very minor and looked like a comment would have sufficed. It didn't address the other issues in the answer. The question itself looked more like a bug report that became very localised once the bug was fixed so action on the question itself would have seemed more appropriate.
Once I'd seen those two thing I thought I'd got the edit figured out and I have to admit in the face of those observations I didn't notice the comment pointing to the other answer from the same user. It is extremely unlikely for me to see the "not an answer flag" (as a regular user there's no way to see edits and flags side by side, I don't think mods even see this unless you make it explicitly clear) that went with that other answer which would have made things much clearer.
Normally I only read the message if the edit makes no sense on first reading. In this instance I thought I understood the edit just from the diffs (there are quite a lot of edits which are basically just comments/replies). The learning point for me I guess is that I should probably make "read the message" something I always do before hitting reject, not something I do when I read the edit and think "WTF".
I'm wondering if perhaps putting the summary next to the buttons would actually make more sense to encourage this, as half the time the summary is off the top of the screen. (That would be a feature request or a question on ux.SE possibly)
Personally though in this case I'd have expected to see this information edited directly into the existing text, e.g. alongside the bit recommending downgrading or as a comment. If I'd spotted that I would probably have hit improve rather than accept and integrated it directly, fixing some of the other issue too rather like Jacques Cousteau did.