It's common on many BB-style discussion boards to edit the top post once an answer has been found, because in that sort of system, useful answers are inevitably buried in the middle pages of the thread, in between initial clarifying back and forth and then fifteen pages of "me too" and "I had the same problem but..." and completely off topic drift. So, editing the first post is the helpful thing to do, because then some future visitor doesn't have to wade through all that muck find the solution.
We don't have those problems with the Stack Exchange engine, but people used to that convention still do it, even more so because we make editing posts a first-class wiki-style thing to do.
So, when someone makes an update like that, should it be rolled back? (Example here: http://photo.stackexchange.com/posts/16850/revisions). I kind of think they should, because otherwise we're not showing off Stack Exchange to its full advantage. Having answers as answers and questions stay questions makes the site nice and sensible and clean.
On the other hand, I hesitate to roll back someone's change unless it's egregiously wrong. It feels like a wrist-slapping kind of thing to do.
What's the group consensus / site policy on this?