Calling a group of women "you guys" is different from calling a person of unknown gender "guy" because in the former case the gender-neutral usage is the only possible interpretation, whereas in the latter it might either be gender-neutral usage or an assumption of the commenter's gender. Given that this ambiguity is nearly always a distraction from the primary purpose of the conversation (as it is here), rightfully or not, pragmatically it is better to use terms that steer clear of it. See Bryan Garner's Modern English Usage for fuller advice on safely navigating this linguistic and sociocultural terrain.
> I don't want to be overly semantic or PC on HN
Proceeds to be overly semantic or PC on HN...