Forum is a forum. Anyone can go back to any topic. I just drew attention to the fact that under certain conditions the main page may look a little strange.
... But only for a few moments. Then there is enough going on to get it into the background.
and if you try to reply in an old topic there is a capcha to bail out lamers, so you should only add to a discussion if you have something new to say.
... and then it is worth to be put on the frontpage.
Since we are in the internet, and against filters/censorship everybody has the right to speak/write, and to be heard/read.