Jacke is bar none my favorite trainer across both classes and jobs, so I was really glad to see him return in the ninja quests. I enjoyed the overlap Averax is referring to as well. Honestly, though, I love all the occasions where events are cross-referenced or NPCs make unexpected appearances, like the stray showing up in the AST quest. Not many of the trainers were memorable for me, but nothing makes it feel like you've actually done things quite like someone saying 'hey, aren't you the one who ___', or 'how've you been since ___?', so I'm all for it regardless.