Out of pure curiosity, what is so taboo about replying to old threads? I assume people do it at least some of the time because there's an interesting point buried in there.
Some boards like you to start a new thread, and link to the old thread if you have an update. But I wasn't really objecting to useful updates. I was commenting on several recent postings by new members with under 5 posts, and they are commenting in 5 year old threads, by adding comments such as "I'd like this".