Ok, Ben, good to know this.
So remoteSort (at least in the Ext's store) is defaulted to false, not sure about Labkey's (it does not seem to be mentioned anywhere otherwise) and I do not even see the remoteFilter config option anywhere :( (Neither Ext, nor Labkey docs...)

Well, the sorting bug I was having seemed to have disappeared (on its own?) even without specifying these two config options you mentioned - last week it was misbehaving... Either I am seeing such "ghosts" for the second time now or I'm going delirious (or might be some kind of caching may be...)