It seems that sometimes, a comment is better than making an answer. I know (now) that moderators can convert an answer to a comment, but the process seems a little backwards. You have to KNOW to flag your answer to be converted to a comment.
My suggestion is that everyone be allowed to comment. Users with the appropriate amount of reputation (50 right now I think) are added to the question/answer immediately as they are now. Comments from users that do not have that much reputation must be approved to be attached.
Who should be able to "approve" these comments? My suggestion is the owner of the question/answer and the moderators. This would take some of the work off of the moderators and puts it on someone who does have an interest in the quality of the question and answer.
I'm sorry if this has been a topic of discussion before, I did a search and didn't see this specific suggestion before.