Seal of Corruption (Horde Paladin) buff is dispellable, but Seal of Vengeance (Alliance version) is not.
Seal of Corruption is showing as a dispellable magic buff, when all Paladin seals were changed in Wotlk to be physical, undispellable buffs with wotlk (every other horde paladin seal is an undispellable, physical buff).
Here’s a screenshot:
https://imgur.com/a/ktzkxiF
Seal of Corruption was added as a new spell in prepatch, so it seems it was just incorrectly classified as magic when it was implemented.
Please fix, very annoying to have to play around this with the multitude of new (and old) dispels many classes have in wotlk.