I really don't mind seeing tags on character's names.... unless I find it really unnecesary. What I mean is, if you're obviously playing as a lion, with the mane and the tail and the features, there really is no reason to put "M Lion" or "F Lioness" in your name. I mean it's obvious you are a lion, with that big fluffy mane or that lioness apperance. It's not like someone will mistake you for a tiger or something... but what do I know?
Out in Bonfire Island, whenever I see people roleplaying as horses I often times see them with "M Stallion", or "F Mare", or "F Filly" etc. Stallion, mare, colt, and filly are pretty explanitory when it comes to what the gender of your horse is. If you put "stallion", or "colt" then there is no need for the "M". Just like there is no need for the "F" if you're a mare, or a filly. Everyone knows that stallions and colts are male horses, and mares and fillies are females. It doesn't take an animal biologist to know that. But who am I to argue with individuals who want to make sure that people know what their gender is? I tried telling them that logic, and they pretty much went "OMG I dont care!"
I think tags are fine if someone is roleplaying as an animal that people aren't too familiar with; such as jaguar, margay, bobcat, jaguarundi, dhol, tankui (raccoon dog), jackal, prairie dog, bear, porcupine, otter, rabbit, weasle, skunk, hawk, owl, ect. That way other players will know what kind of animal species is near. Like from time to time I will see an owl character up in a tree and be all like "Hey lookie there. An owl!" Just to acknowledge their species and their presence.
So that's what I think of tags.