not sure whats wrong with guesses specially if there's a disclaimer saying it's his guess, actually...

otherwise, might as well not think of comment at all, since there would be nothing to say. (that goes for many, many other topics)

Guessing could get a random employee at GitHub who is completely innocent targeted with a lot of hatemail he didn't deserve.

Just because someone says "I'm guessing", doesn't mean people wouldn't roll with it.

Don't privilege the hypothesis.

http://lesswrong.com/lw/19m/privileging_the_hypothesis/