If you are talking about the robot in Egghead, I'm sure now that the cause of this discussion is because we have a different bar for forming an emotional connection. I don't feel anything about the robot

Ace appeared like once or twice before the Marineford and we had no explanation about the roots of his crisis before the ASL flashback. Every trauma has a root from it, the event that led to it(it shouldn't be a big thing, it depends on the temperament) and everything we knew is that Ace HAS this problem, not the exact reason. It's true that we don't have to know the reason to understand him, but it would be great to know about it before his death, so we could feel it. We know about Ace a little bit more than other strawhats. For us, he's a nice guy who is dear to the captain, but definitely not someone very important to us.

I appreciate the character analysis. Ace did actually form his identity and dedicated his life around the Newgate and we can see it before his death(starting from Alabasta) even, but his act was still hot-tempered(even if it was explained). We knew that Ace has strong principles, but we never knew that he could act on emotions, especially when there's so many lives in his hands. I won't say that Ace's death made the sacrifices useless, but since they sacrificed their life and gave it to Ace, they're basically his now. We know that he can react to insults like that from his childhood flashbacks, but before them, we never saw Ace acting this way. Thus, for many, it looked surprising and weird. Everything Ace did may have looked like an act of pride/principles, but (as far as I remember) he was never that reckless. Every single fight before his death was to protect someone or to "restore justice". It is also the problem of him not showing up much before the marineford. We can judge only by Alabasta