I will go first by adding an example that @Minh_Nguyen provided in the Landcover V2 proposal announcement discussion:
What I most appreciate about this discussion is the awareness that land use is orthogonal to land cover. I regularly encounter confusion on this point not only among new mappers but also among experienced mappers who, for instance, argue for cutting a hole in a
landuse=residentialarea to accommodate a lushlanduse=grassin someone’s front yard, or for cutting up thelanduse=residentialarea into tiny chunks criss-crossed by yet-to-be-mappedlanduse=highwayandarea:highwayareas, or fractalizing alanduse=residentialto exclude parts of residential buildings merely because of some overgrown trees. Confounding matters are the non-landusetags likeamenity=hospitalandleisure=park.
I hope that this is giving an example of the kind of controversial / unclear mapping situations I am looking for which could be adressed by future solutions / consensus.