Is HK-51 a... retroactive (?) character? Meaning if you pick him up at 50 you can gain his affection and companion cutscenes I'm assuming and stuff like normal companions right? But if you get him earlier on in your class story does he speak during class quests and react to NPC dialogue like your other companions?
If he does I might save him for my new trooper, but I would want to know what he says in all of the 8 class stories.
Considering he requires a character on both sides, I'm more curious to know if he is a "legacy" companion (once you unlock him, he's unlocked for all toons).