@Triceron:
I'm not saying the Strawhats should kill people, just that death remain permanent and not simply be 'oh character X was hit in the heart and we all cried but he got better'. The whole series set the tone from the very start with character death when Shanks' crew member offed one of the bandits for threatening them with a gun. Characters have died in most every character backstory, but it's usually all history.
I know it's still a kids series and death is a difficult subject to tackle, but it's also a big part of feeling the unpredictable nature of the world.
This topic has been brought up and talked about a lot. Many of us are/were disappointed to see Pell survive after all that build up; but if it doesn't affect the story, I say we should give it a free pass. It's not like there wasn't any advantage in the long run. I do believe Oda's trend of not killing off characters gave Ace's death that much more impact. It was unexpected for most us and at the same time, it was crucial for plot progression. Besides, random fodder seem to die all the time even if its not explicitly alluded to. IMO, the reason for this is the same as the reason why characters dying in the flashback isn't a problem; its that the fandom(especially the younger readers at whom the series is aimed at, like you pointed out) hasn't had time to 'connect' with the characters. When they see Impel Down prisoner #451 die of Magellan's poison, they couldn't care less. But replace this with Bon-chan or even Crab-chan and its a different cake altogether. That's just my take on this.
Would I like to see a greater amount of ambiguity as to the fates of main/supporting characters? Yes.
Do I think its absolutely essential? Not really. But meh, everyone has their own opinion on this issue.