Sometimes the OP is trying to describe the problem with terms that can't be said usual, maybe because he's expert of another application or maybe he's not expert at all. The result is a maybe well written question, with picture showing the problem, but lacking of those keywords that are immediately capable of exposing the issue.
One of the latest example could be:
From now on I will refer to the title, but the same can be said for the content in the body of the post too.
The title doesn't give any help in describing the problem itself, it just mentions a face. It can be almost anything, and I may guess it will be shown in the seach page when someone will look for a solution to a problem related to faces, with all the other question with titles like that.
Should I edit it to better specify what the post is about? Or should I leave as the OP wrote it?
The editing page of the rules says to feel free to edit...
... any time you see a post that needs improvement ...
but I'm not sure that editing that way would be an improvement of the post in global terms.
I personally don't find titles like that useful, because they are not saying much about the issue. I'm not inclined to look into the question (but I was curious.. eheh), I would change them all believing that this would make it easier to anyone to choose where to spend our time in aswering or finding a solution to our problem.
But maybe for someone who don't even know those keywords, someone who shares the same level of knowledge of the OP about the topic, those are the right words, those are clearly describing the issue the way he would have done himself. Also, knowing what the problem exactly is about, is half, if not more, of the solution. Heavily editing the body in this sense would be basically answering the problem, but there's a dedicated space for that.
Here's some links I visited while trying to find an answer: