No, they're a symptom of the different UI in forums. Mailing lists are generally presented as a set of threads with any unread posts being highlighted. Forums are generally presented as the set of recently modified threads without any immediate visibility as to the posts within them. If you post to a forum there's a good chance that people will miss your post entirely simply because they're not checking the forum frequently enough. Different UI results in different cultural norms, and trying to merge the two leads to disasters.