The current requirement for proposing a tag synonym is five score in that tag. Would it make sense to also allow people with accepted answers to make proposals, even if they don't clear the score hurdle?
An answer is accepted from a user because it helped him more than the other answers. Between an answer with a score of 5, and another answer with the same score that has been accepted, there isn't much difference in term of quality; it just means who asked the question preferred the other question for any reason: Maybe one question contained example code, while the other didn't use any example snippets; maybe the accepted question was given from a user the OP trusts better; maybe the accepted answer was more understandable from the OP because it used words that were more comprensible for the OP.
So far, I have seen accepted answers with a score of -2 or lower. In this case, the OP (a single user) accepted the answer, but 2 or more users down-voted it. I think the two down-votes count more than the answer being accepted.