I've spent some time thinking about this. I know I used to be nervous about apping male characters on new games because of the stigma I expected as a cis, heterosexual woman playing gay or bisexual men. But I eventually got over this because I discovered over time that as long as you demonstrate that you are playing people who are people first, as opposed to sexuality-shaped kinkboxes of whatever dimension, people who are worth RPing with will RP with you, and people who are assholes will be assholes.
I do play a lot of bisexuals. I can be a boring straight white girl in my real life, there's no need to explore that in my RP. I used to play straight boys sometimes, but eh. I've written a few ace characters and received occasional forays into people who don't "get" why you would do that or I guess ... want to "convert" your ace character, which isn't really how anything works, but people do it to real ace folks all the time so I guess it's ... verisimilitude??
On Arx, did run into several people playing (or playing about) nonexistent homophobia, similar to people playing or reacting to nonexistent sexism. Frustrating when people try to sandbox away the parts of the theme that make it interesting and/or enlightened.
Mostly, otherwise, I've lately played on a lot of small games and haven't gotten a lot of shit OOC or IC for sexuality-related things because I'm largely playing in small groups with people I trust not to be assholes. And occasional issues with, I guess, bizarre and idiotic rumors being spread about me and the sexuality of my characters behind people's backs, but it's got the T-shirt on that at this point.