I do the same (when I remember to, that is), though in this case, I was actually referring to the fact that "gnostic" and "gnosticism" are only capitalised when referring to particular sects of Christianity, rather like how "communism" is only capitalised when referring to a proper Marxist regime, not the over-arching belief in the abolition of private property.

BTW, if you read the article all the way to the end, you might notice something a little strange. In the English translation of "We," the word "reason" is capitalised for a similar reason. The full sentence is "Потому что разум должен победить," which means "Because Reason must prevail." If you've never read "We," you should.