I find it wrong to do anything that in essence reduces anybody to something as trivial as their sexual orientation, but I admit occasionally being referred to or referring to others as "a/the gay (one)" can be slightly endearing if not taken seriously.
I don't know about that but within our friends we have two Jay's one white and one black. After a while the black Jay said just call me BJ and it stuck for 15 years now. He likes it more than Jay. I don't have two friends that are gay with the same name so I would never use those terms. I am not gay so I guess if someone called it the gay one I would not understand why or even care.
As for other people, like someone mentioned above, I will always try to say, Sam Smith, the singer, or some other trait before resorting to the gay guy because it's probably likely that if they don't know him as a singer they don't know he is gay either.
So annoying. I'm always the "gay" one whenever we compare our group to famous people or characters. Others get judged on personality and me on sexuality.