Now that I see the pending edits, I come across such suggested edit - since I can't know for sure that anonymous user is the author "pat1234" I've rejected the edit - what if it's just some troll?
What are other people here doing in such cases?
I don't see a problem with that your example. The question 'belongs' the the community, and the edit was making it more precise.
In this particular case, I strongly suspect that pat123 asked his question from work, then added the edit from home where he didn't have his login credentials to hand (or he's got a cookie-based login). Anyone else editing it that way would be highly unlikely, especially as the question already had an answer.
It would be slightly more suspicious if the answer had been marked as accepted, but that's not the case.
I see a lot of edits like this as well. Unless it's some kind of improvement like adding a link to a keyword or something like that I reject the edit.
Some of the suggests are actually new users who are mistakenly trying to ask for clarifications by editing the answer. However quite a few of them are users browsing the question and adding their opinion on the matter.
My feeling is that this situation is a difficult one with no easy "rule of thumb". If it seems quite obvious that:
I'd be inclined to approve the edit. If I was in any doubt, I'd reject the edit and add a comment to the question with the meat of the edit (where posible - this would be quite hard to do for anything other than an addendum), so that it isn't lost from view as it may be genuinely useful and from the OP.
Edit: In this example, if you've over 10k reputation, you can see that there's a deleted answer from another user named "pat1234", sharing the same auto-generated gravatar (id: 777758 - as opposed to the OP who is id: 777658) which would suggest that the OP is genuinely unfamiliar with how Stack Overflow works and is thus quite likely to not have a handle on creating their account properly.
This only serves to reinforce the "theres no rule of thumb" point as context is everything with something like this.