I think the most pervasive troublesome thing when it comes to sexuality and gender identification on MUSHes remain the folks who are very centered on wish gratification and fetishization especially when those are deeply enmeshed. I mean you have the often misogynistic creepy dudes playing lesbians issue that seemed to be all the rage to the point of being a pretty good assumption in the 90s, but there have been other instances (ooc female yaoi fans dominating portrayals of gay pcs, some uncomfortable encounters I have had with people portraying non-binary or trans PCs when it was clear that there was some ulterior stuff going on, ect.)
There is often denial or accusations of people being too sensitive when something seems off, though I guess no worse than other parts of the internet.
I do not know that it is better or worse in mushing. My kids (16-almost 18, who are all rpers but do not have interest in mushes because of the real time factor) and I have frequent chats about this and they report a lot of the same behavior to be honest, even though their places are filled with peers or close to it!