There are a lot of the sort in the Jossverse - Angel/Angelus, Willow/Dark Willow, werewolves. The conflict usually rests on the character being terrified of reverting to the alter-ego and endangering others, although the alter-ego doesn't care and will continue to rampage until checked by outside forces. That's not how it worked with Mr. Hyde, though. Jekyll deliberately created and became him, and there was no surplus power that went along with the Hyde form; it simply had the benefit of not being recognizable as Jekyll and thus left him unaccountable for its crimes. He himself decided that Hyde was someone else, so he didn't feel guilty in either state: Hyde wasn't capable of guilt, and Jekyll wasn't the one doing the things that should make him feel guilty. As the article says, that wasn't an outlook that reflected reality: Hyde was Jekyll, just in a different body.
I read the story a long long time ago, and while I'm pretty sure I can say that I didn't get it at the time, I do remember thinking something along the lines of "Hey, why is he still drinking this potion? He knows he's just going to go out and hurt more people, the jerk."
But, years of ignoring the whole point or not, this is still one of my favorite morality puzzles. Jekyll and Hyde was the first musical I ever saw, and it was stunning. Part of what I enjoyed about the twist on the original, in that case, was that Jekyll was a noble but idiotic scientist, and the narrative refuses to explicitly say so. During one of the songs at the beginning, someone on the medical board or whatever asks him what happens to the evil if he succeeds in separating it from the good in his mad experiment. Excellent question! Nobody bothers answering!
So, the story of Dr. Jekyll being an asshole who doesn't want to own up to his crimes has never been replicated in its modern tributes, it's true. But he wouldn't make much of a hero, so I'm glad we got the versions we did instead. Take a look at Angel - knows what's going to happen if he takes the metaphorical potion, knows he'll be happier, won't feel any more guilt, won't suffer any consequences at all. Also knows he'll be a killer, so he won't do it. It's not about him being a killer; it's about people being killed. That's why Oz keeps himself locked up even though his transformation will be temporary and he won't have to deal with any memories of it. That's why Bruce Banner doesn't want to show anyone "the other guy".
I love the way Whedon characters get us talking about the nature of good and evil, but one aspect that always seems to get left out is the relevance of danger to our choices: there's a lot of things we can do that could make us feel good or bad, proud or guilty, without ever making much of a difference to anyone else. Once you expose others to something that could harm them, though, all bets are off. There's no Hyde until you give him a name and set him loose, and that's when Jekyll ceases to exist.