Part of her - the almost military manner, the strong suggestions that she's a life-long bachelor, her dogs - fits in with a type of woman one encounters at times in British books (not so much in books from elsewhere, though ). But generally those women are tough but fair, and think highly of sportsmanship (in sports or elsewhere). McGonagall fits the description almost to a T (funny expression, that), and in books like Enid Blyton's or Agatha Christie's (yes, so I read much more of those than of actual respected literature, sue me ) there's tons of these women.

But since Marge is Vernon's sister here, Rowling seems to omit the tough-but-fair thing, and gives her a mean and petty streak instead, and lets her cuddle and shamelessly spoil Dudley, which makes for an odd combination with the rest.

Her motives are unclear as well, I agree. Neither her apparent love for Dudley nor her hate for Harry make too much sense (though obviously Vernon will have told her all kinds of lies about Harry). Some people simply like to pick on others because they're bored or to make conversation, and I guess Rowling made her like that.

It's definitely an early sign of his troubles keeping his temper under control, which will keep getting him into trouble until very late in the series. He had full justification, but then he often does later as well, that's kind of besides the point. I wonder if Rowling was already planning that to become as big a problem as it does later...

Yeah, not very flattering to Neville, that. Harry respects Neville more than most people do, but still not very much yet at this point, I dare say.

I think the Dursleys for all their mistreatment and abuse of Harry are still reluctant to kick their cousin out or refuse to let him come back. It's only when his presence there starts to actually endanger the rest of the family in book five, that kicking him out is on the table.

Yeah, his pomposity and patronizing attitude are clear here, as is his tendency to shy away from difficult problems.