Theoretical question, then. Let's assume, because I don't know, that one month is maximum time to allow for new replies before thread is no longer allowed replies (BTW, forum could benefit from auto-locking add-ins or notes saying the user is replying to a very old thread, I've seen these used). Someone posts a new thread after 23 days. It's locked because of the other thread. Other thread is replied to 10 days later. It's closed for being a month old. Why not merge and save the trouble? :)
You can't hard-delete posts? Can you please suggest to the powers that be that users have the ability to hard-delete their own VMs that they accidentally post to their own profile? I have so many I've had to delete self-posting to myself. In fact, to keep one's profile clean, it can be handy to clean up old discussions; having the option only to soft-delete leaves quite a mess...