If a homosexuality gene lowers its own probability of being reproduced today, and yet still abounds in the population, that is a problem for commonsense as much as for Darwin's theory of evolution. And, intriguing as several of these theories may be, I have to conclude that it remains a problem.This Dawkins FAQ page is fun reading, but I particularly enjoyed the discussion of how homosexuality fits with Darwinian selection. On reflection, though, I wasn't that impressed with Dawkins reasoning. He ought to have begun with an analysis of whether homosexuality was unique to homo sapiens, or whether it was also common among other primates, mammals, etc. It it's seen in other primates and also non-primates, then most of the explanations he advanced are unlikely to be true.
I'm inclined to the theory that there have been very substantial benefits to human and other animal societies from genes that, at least in some men, have the "unfortunate" (from the gene's perspective) additional effect of preventing reproduction. It's interesting to know this is an ongoing mystery however.