Liferay does some spam checking to keep spurious crap out of the forums. I believe your forum post count may be a factor in determining if something is spam (i.e. I think if I posted the exact same message, it would probably go right through) although I don't know any of this for sure.
You might try with a simpler version of the post and reply adding on the other content until you get the whole thing onboard. Otherwise you'd probably have to get James Falkner to do a deep dive and figure out why it is spam and fix the calculation...
