Sorting on field of Model Types is apparently messed up

(Bug, Closed -> Fixed, Priority: Critical, Test Status: Unit tested , Reported By Justin du Coeur, )
Functions
Summary: See this page for an illustration of the problem -- he has a List of Model Type, which he's trying to sort on the fields of that Model, and it's not working as expected.
(Reported by Xavier)
He's confirmed that sorting on dates and numbers separately works as expected, so the issue is very likely something to do with extracting them from the Model Type.