Hey asy concerning the straight guy who was wanting to write widowtracer I feel his pain. As another straight male widowtracer fan I tried to write a fic and I got criticism for not being gay or lesbian so I never posted it. I just wish others in the fandom would believe that we love this ship despite being the majority and opposite sex. Just had to vent.
“You must be X minority or you’re not allowed to write about characters of that minority” is separatist thinking. It’s understandable, I suppose - minority people are so used to majority people badly writing and poorly representing their characters they find it hard to trust anyone not of x minority to write them!
However, unless people are always only going to write about themselves, this sort of thinking is a little myopic. If you’re a straight cis guy and you want to write lesbians that’s fine - but be respectful, think about who your audience is (hopefully other fans of the ship who are mostly queer chicks!), do your research, listen to appropriate feedback and consult with people from x minority to make sure you’re getting it right. If you’re doing all those things there’s no reason you can’t write a great lesbian story despite not being a lesbian yourself :)