Possible Duplicate:
Allow flagging a Comment after voting it up

Once you've upvoted a comment, it's impossible for you flag it.

It should be possible to flag it as obsolete: a comment can be upvoteworthy at first but obsolete in light of later edits or comments.

marked as duplicate by BoltClock's a Unicorn Feb 28 '12 at 18:48

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.