I like this idea. In particular, I like the idea of analyzing content - but not programatically rejecting the post completely. Another forum that I frequent tries to keep things civil by banning certain words. Sounds good on paper, but then you try to use the phrase "knee-jerk reaction" and the system rejects your post because it has "jerk" in it. D'oh.
Pointing out the possible (but not definite) incivility, but allowing the post anyway (after a confirmation step) could be a nice way to remind people to be polite, but without being overly draconian.