Another issue I've run into is the minimum numbers of characters needed to edit an answer. Once I found the answer that was chosen and upvoted had code that didn't make any sense. It was something like an instance of a point object "point1" and an instance "newpoint" and they wrote "point1 = newpoint;" but actually meant "point1 = new point();". When I realized the problem I tried to change it but wasn't able to because I wasn't changing the answer enough (I think there's a minimum 6 character limit). I didn't want to make random changes elsewhere just to make the minimum needed to fix it, so I let it be.
I find Stack Overflow useful, but I don't try to participate in it anymore and don't stay signed in.