Having forgot to take screenshot...
Permanence potion effect ended a few minutes before I reached the NPC to turn quest in. Although the effect was over and I should've gone experience point for the quest, it still showed among quest rewards I wouldn't receive experience. As I said, the effect was over already for five minutes by that time, so it should've shown xp amomg rewards too. In the end I didn't turn it in, not to accidentally become one of the poor guys whose work was ruined by a little mistake.
Anyways, I would like to ask: Would I have received no experience point for turning in that quest, or is that a bug that still needs to be fixed to prevent accidental level ups?