I come across this scenario occasionally when I see a question which has been closed ("to prevent 'me too' and 'thanks'), and the existing answers are either unclear, or are wrong. I notice this in the StackOverflow section where technology changes, and the existing answers are right for the time period when it was answered, but wrong for the current time period. Or maybe the answers are correct, but I might have a new answer which isn't addressed elsewhere.
Other times, I might not have enough reputation to answer.
The only solution in either case is to ignore the question, or to answer as a comment. I'm against preventing answering when there is not enough rep, but I don't really know the history behind that design concept. I do get the concept of closing a question to prevent spam, me too, and thanks; but really, if I have a legitimate answer to a closed question, that robs the community of contribution. And still, comments can be entered as "me too" and "thanks", so the purpose of closing questions to prevent me-too/thanks answers has not really been addressed anyway. And open questions can also be answered with me-too/thanks... so really, what does closing questions do for anyone?
If someone answers in a comment and they don't have reputation, and the comment-answer is worthy of a bona fide answer, can the moderators bump the comment to an answer? Or flag it to be automatically bumped when the commenter eventually gains reputation to answer? Or must they resort to leaving yet another comment to the commenter, suggesting they answer it (which they might not be able to do if the question is closed or they don't have the reputation).
Otherwise, I completely agree with slugster: the problem doesn't seem rampant here, I think, so maybe best to let it go until it becomes a problem.