I suggest to stop these thread creations, feels like spam. The new joiner(s) most likely does not even know, or most don't care, or don't want to intro themselves, so it's better to them take their own initiative to create their own "Hello, world!" introduction threads. So far the few I've seen, they don't even respond to your automatically created thread and welcome message.
I would instead recommend shooting an automated private message to them, with the link to direct them to the correct sub-forum for self introductions.
