Unique - Only one copy of this card may be in play at a time.-Koey
I'm not happy with this one - if you control a unique character, you may not play another one with the same name. For that purpose, having a unique character in Command counts as controlling it. ("control" isn't the best word - better one?)
However, you can have more than one unique character in play - each opponent may have the same. Additionally, you can control multiple unique characters if they weren't played from hand (raised from graveyard or played while out of game)
All Aleta are special - they are hardcoded to never permit more than one under a player's control. If you lose an Aleta, play the same from hand, lose that one again, play a new one etc... when the first Aleta returns from the graveyard, it will die at the end of the turn (and cost morale again). You can suicide yourself with Aleta
This has been a while since I tested it, that might have been fixed... But I never read anything that would affect Aleta's rebirth.