cometary debris explains continent sized wildfires

http://www.ras.org.uk/
13,000 years ago there is reason to believe, per the article linked above, that not a huge comet, but a cloud of tunguska sized comets in a swarm, as in a big disintergrating comet, hit North America. Apparently there is evidence for a comet entering the inner part of the solar system 20 thousand years ago, and this event would be part of that event. I guess this also explains the 12,300 year ago event which so recently was discussed as leading to the extinction of many north american mammals, this may be a refinement of that, I am not sure.
This idea is supposed to address the issue of the unlikelihood of one huge comet hittng the earth so recently. Now I kind of get the wild fire business, (read the article) but just because something is unlikely, it doesn't sound like a very logical reason to reject it (assuming thee is other evidence). But this afternoon on npr they were interviewing someone who said it was beginning to look like our solar system was NOT so common, because they have now observed so many Jupiter types in other solar systems, where the Jupiter type planet is formed far from the star it orbits, but is drawn closer to the star, which of course would eliminate the inner planets like ours. Anyway the guy was talking about how uncomfortable it would be if it turned out the earth was in a very unusual solar system. What is that uncomfortableness about?