I'm sure you can define the problem narrowly enough that it's impossible to improve on randomness.

Is it fair to call it "logical rudeness" if someone just doesn't notice that you've made a point?

Answered here; this seems to have been the case. (I disagree on the 'switching sides' view - that idea seems not to be constructed in a rational way.)

It would be nice if forum software (especially here!) had a flag so that commenters could say "this is a point in need of answering", and others could be alerted that there was a point which hadn't been answered.

This sounds like a very good idea.