Nothing to stop you from continuing the topic.
Actually, I think there is something from stopping us from continuing.
Often times, I have been interested in dicussing a topic, and the discussion has gone quite well for a few posts, then someone makes a post which is contraversial which takes the thread in a different direction on the same topic. Trying to continue the original discussion becomes futile, and in some instances, causes more outraged posts. My greater investment lies with relationships rather than the topic I'd like to discuss, and so I give up on the topic rather than risk bad blood. This is what stops me from continuing, and it's a shame because it means that many topics end up being dominated by people who shout the loudest.
In the past, I was often a hot-headed, run-my-mouth-off knucklehead. Nowadays, I'm not interested in arguing (even when I'm right, which is most of the time
). Also, it's way easy to misunderstand someone on a forum on account you can't see folks' expressions or their voice intonations/inflexion, so I tend to just sit back and let others fuss.