hc shows r odd, i like em but where n why do everyone do that dancing style, not dance but like fightin air. i just be g walkin to the drums n shit,hc drums r fire, but the hc peeps dont dance to the rythm. why people do that? is it monkey see monkey copy thing?
a great poet once said, "why is the sky blue? why is water wet? why did judas rat to the romans while jesus slept?"
in all seriousness it's a long story that runs from 70s punks doing stuff like the pogo and skanking, and it runs up through all kinds of regional and stylistic variations today.
maybe i have an NY/NJ bias but I think most of the karate mosh you're talking about is from people who learned it from videos like this