@echo I think it would be lovely if it did.
@echo I like learning things, so yeah, skin tones would be nice. If there are settings, make it togglable.
it may actually be the most beneficial to just have the Unicode emoji itself as the alt text, now that I've talked with some people. but still interested in thoughts 
@echo Having the Unicode emoji as the alt text would not be helpful, as it might not be read correctly or could appear distorted— I once had alt text be read as U1F34B on a U1F350 (instead of lemon/pear emoji). You can use the emoji name and specify the skin tone if a non-default tone is chosen.
@echo I would expect the skin tone to be present. If someone went the extra step to chose the non default tone, for this message or on their whole OS, it might be because it matters to them for the emoji to be viewed/described as such