I don't know if this is a PROBLEM per se, but whenever I come out to someone, they're usually like "oh, i knew that from the first time I saw you" or "well, that's obvious, i mean, you're practically a guy!"
It used to bother me, and it sort of still does, that people think lesbians have to look like guys, and if a girl dresses masculine or whatever, that automatically makes her a lesbian... but, tbh, I find it really funny when I get that reaction now, coz it's just so dumb!