don't think it's worrying -- it's just "remove best effort".

only worrying thing would be cases where caller relies on removal.  don't think there's any way to test for that however (unless we have a "finished map" which we can mark finish once we've dealt with it and warn if the caller does anything to it subsequently ... but think that's overkill).  we don't want to log warning simply because the map is mutable, or immutable, as either of those are fine things to do most of the time.  personally i think we should refactor to take a config bag in time then warn on the old (map) path though it's hardly a big thing.