Is also depends how old the original thread (s) on the topic are. If there is some thread about a topic that already exists, but it is a year or two
old then of course there needs to be a new thread made. But if the new thread is made within hours or even a month or two from another one then yea,
the poster should probably just add to the existing thread unless to do so would derail the original thread too much. Of course that is all my
personal opinion and nothing more.