The
rules are clear. When you use the /marriage command and accept a marriage proposal from another character you automatically get the same last name as the male character. Why not the female? Beats me. Feel free to start a new thread about that but it will likely not achieve much.
Same sex marriages are not supported by game mechanics so you cannot get the same last name with the /marriage command. All cases not included in the range of this command are not going to be fixed by GMs. This is not a bug. It's the way the game has been written, so deal with it. You're not a jedi either.
RPing a marriage (of any kind) is definitely not the same as RPing being someone's sibling/parent/child. When we allow players to get the same last name because they RP being siblings or whatever, it's a permanent change. Whatever happens to their characters, they are related forever from that moment on. In the case of marriages, you never know. That's why there is a /divorce command (and, of course, it only applies to the cases where the /marriage command can be used).
In any case, same sex marriages are really outside the boundaries of what the rule states as exceptions to changing valid names. So, no: the rules have not changed and until further notice from the Settings team regarding the issue of same sex marriages, the boundaries of the /marriage command will remain the same.
Does that mean you can't RP a gay character? No. Of course you can, unless homosexuality is removed from the settings as a whole, like vampires, Roe vs. Wade or warp speed, which, by the way, would be a creative choice of the writers of this game (and it is, of course, their prerogative) and not a political statement that reflects their personal opinion on these issues IRL.