Since 2018-12-11 patch, if Whitemane takes Clemency at level 4, when she casts Inquisition on Cho’gall she will be refunded no mana, regardless of how many stacks of Desperation she has.
I dont know if its related to certain heroes or not, but it happens both on offensive casts (Inquisition) and defensive casts (Clemency). It clears the desperation stacks, but sometimes it does not refund the mana.
It happens when you cast it on heroes with no mana, Fenix Chogall Valeera etc. Needs a fix asap
We have some tracking in for this as well, thanks for the heads up.