I agree with the others who said that accents are to be heard, not read. Subtle reminders are nice but, as always, exaggerations are annoying. If Krum talks with a 'thick accent' every sentence, I end up seeing him trying to talk through a mouthful of stew.

Also, don't take offense, but most of the time accents are way overdone. I'm French, yet when I speak English I don't mispronounce every second word.