I have to chuckle when someone comments on a picture of a quilt that was posted several years ago. Then several other people, not realizing that it is an old thread that was suddenly brought to the top, comment also. There's no harm done, sometimes it gives new life to an older quilt, and gives new members a chance to see it. Of course if the old post you want to comment on is one where someone is asking for help on something, you're probably too late to actually be of help. If you have something new to add (a new technique, for instance) it's probably better to start a new thread in that case.