I would allow same-sex-marriage ingame... it would have to be done at some kind of church or temple and i would also allow krans to have any marriage they want to, cause sex isnt limited to penetration, so it means even krans can have sex (oral, or anything you want to imagine...)
i wouldnt call a player having characters in different marriages, being in polygamy, cause each of the characters is in monogamy...
here all that counts is the ingame-character/in-character...
same-sex-marriage might be hated by some factions, but their characters might handle that their own way...
maybe a priest of talad would hunt those, but others would protect them...
you'll never know...
at least it shouldnt be deactivated, cause that would limit the Roleplay.
a marriage doesnt need to be something done in public...
for a marriage you only need a priest and a partner...
its the first time i'm worried if a female char is played by a female player

i only play female chars in singleplayer RPG-games...
and different from my own taste, my chars like fluffy things or pink stuff, or just anything i wouldnt like...
you need to keep that in mind when playing, that its not really you...