There are different points in your question
On Stackoverflow there was a very ambigious and poorly written question, which got edited by me and a few others. Now that we edited
the question and made it clear and understandable there was a upvote
So the post you mentioned has enough facts/points (but was formatted badly) which constitutes a good question, so that it become acceptable (up votable) after your edit.
If the question has enough information so that it can be answered, he deserves an upvote even if the question is poorly formatted (Especially if he is a new user, which he is in this case). Remember, there are several (new )users asks question on stackoverflow who doesn't know how to effectively ask questions
- how to write title?
- what and what informations are needed for other people to answer your question?
- how to format code?
- troubles with language, not all people here English speaking etc
Community can help them, edit their questions, translate if needed, as long as the edited post is a answerable/acceptable question. Once they become familiar here, then they will ask in proper way. So
Should the user be rewarded for the work others do?
If original question is bad, then no edit saves it from closure/downvoting. In this case the question was good, you made it better. So 5 rep for OP, since it is his/her question and 2 for you since you helped him out by editing out (well until you reach some limit).
you should only get +2 Reputation as long as the question has more downvotes than upvotes, so the upvotes balance the downvotes.
You are down voting the question, not the user. And to a question, only down vote count is important, cumulative reputation value not. If a question got 5 upvote and 6 downvote, its value will be -1, and it is a bad question.