The dead thrall active effect causes every single npc to skip their normal greeting and instead go "Would you mind dousing your magic" every time you talk to one. Asif that was not annoying enough it also overides quest dialogue wich means you often start conversations by responding to questions the npc never asked. Since thralls have an uncanny ability to get stuck or dissapair for no apparent reason leaving you with an undispellable permanent dead thrall effect (summoning new ones does not remove it) simply killing off your thralls before entering a town wont work in the long run. Needless to say this kills off immersion pretty damn fast and i for one would be eternally grateful if someone could create a mod wich causes npc's to ignore the thrall effect like they would a mage armor or muffle spell.