I do not see how stating if you're a male or female with an M or F is quite the same as having your sexuality in your very character name. Your sex or the characters sex and what they actually look for in a romantic/intimate relationship is not something that goes on an even level at all. So if it was only a matter of you feeling the same way about seeing those tags to you I really do buy it, but if we'd be speaking of the general picture it would be far from the same.
To plainly put out the point here, in many situations it's good to write down, tell people which sex you are and instead of rambling up a big list of things I'm sure anyone can just think of situations them themselves have needed to mark down or tell their sex in forms or information fields. Now flip this around and look over how many times you must write out your sexuality to get around, there's not many situations you do unless it might be certain surveys that has anything to do with relationship or needing to point out your actual sexuality.
It shouldn't matter much if you are a proud gay man or woman, as far as it goes on FeralHeart it quite doesn't fit in like it could, and I will really quote what Sura said earlier in their post "What are they after exactly?", there's no great benefits for doing this unless you must hang out with other gay people, and then again, why must other people hang out with other gay people and no one else? It's a bit like a reversed effect on homophobia going the other way around. I'm just saying this to put a point across though, and as mentioned in my first post, I think in a place like bonfire or even the whole game it's a bit more simplistic look of what it means to be a homosexual.
Not to mention that we've all seen our fair deal of people especially Wolves mixing up genders and I cannot recall how many times people have said to another "I'm a male!" or "I'm a female!". On a feline like a lion you can usually tell by males having a bigger or longer mane than "most" females, but also in general(not all) males have slightly bigger chins or muzzles as well. Personally I'd not use M and F tags either for any character but I can see some good usage for it in a game like FeralHeart, and I do not see it as seeking for attention just because you are a female or a male. People just don't mind what sex you are, however some people really might look a second time if you for example are going around with a shirt saying "I'm gay".
It's not like it can be stopped, or that a campaign should be put to stop this either(lol). But I really do believe it's unnecessary and it's really all about yourself if you have a tag like this, compared when a M and F tag really could assist. The bio do suffice well if you need to point out about your sexuality. However I do sense that there's actually another really big issue that could be laying around and pulling strings on this subject it self, but it would pretty much need it's own topic. If you have your sexuality in your name you want a straight and basic approach for something, and the question is really approach for what, and what it is you are seeking or want to achieve with this name, and as it stands in many of the times(Not all though since there's exceptions as always) people are up to mischief with these names.