OK next test complete. Grizzly Bear Man from Dwarf civ, but not player site. Travels to player fortress becomes member of fortress guard.
On unretiring the fortress he's a citizen with full labors available. Can even make him militia captain unlike visitor mercenaries.
I'm thinking that's supposed to happen to performers too. Seems unfair that a bard adventurer can't become a full member of a fortress.
Confirmed, that did it! To be specific. I created a fort, then retired it. Made an elf from a nearby civ, walked him there and retired him. This made him a citizen of the dwarf parent civ for my fortress as well as his original elf civ. It did NOT however make him a member of the local group that runs the site. This made his labors unchangeable when unretiring the fort.
I then read the instructions here about talking to the militia commander on site. So, I retired the fort, unretired my elf, found the militia commander, asked to be a militia dwarf and that made the elf a member of the group that runs the site. I unretired the fort, and blam-o, my elf was a full member, whose labors could be changed.
Interesting to note here that he was from the nearby elven civ that my fort site trades with originally, and yet still became a full, dual citizenship elf of the fort.
Thanks a ton all for the discussion so far!
ASIDE: Toady mentioned in an update that he thought he had fixed the retiring of an aged fort causing merchants and visitors to flood the fort. This has not been fixed. When I unretired the fort, there were two elf merchants and two camels of theirs, all marked hostile in the units list but not attacking anyone, and one human hammerman, also marked hostile but attacking no one. I really do wish that would get fixed, it makes such a mess of a retired fort that you adventure at or in an unretired fort