It never hurts to remember that comments should be made to help in the perception of questions/answers and not to hold a conversation. If you erase the comment has no harm, but if you leave them there then we have a mess and people lose the will to participate because there will a private conversation.

It never hurts to remember that comments should be made to help in the perception of questions/answers, and not to hold a conversation. 

If you erase the comment later, then it is not harmful.
But if you leave them there then we have a mess, and people lose the will to participate because there will be a private conversation.