It encourages dialogue between more than two people, which is often a good thing. The quality of a discussion usually improves when more people participate. It

It encourages dialogue between more than two people, which is often a good thing. The quality of a discussion usually improves when more people participate. It's rarely a problem if someone forgets to follow up since someone else will usually do it, at least if their views are shared by other people. That being said, the "threads" page is useful for finding and responding to new comments in your threads if necessary.