Not my area really (I'm more of a time slip person) but this caught my eye because yeah, I've noticed this at my mate's place. Same corner every single time, upper left near the ceiling. Never anywhere else in the room.
My half-baked theory is that it's got something to do with how energy or whatever accumulates in corners - three surfaces meeting at one point, maybe that matters somehow? I dunno, I'm just speculating. But the consistency is what gets me. If it was random you'd expect them to show up all over the place, not always the exact same spot.
Has anyone tried mapping this properly? Like actually recording which corner in multiple locations and seeing if theres a pattern with compass direction or room layout? Because if shadow figures are consistently favouring certain corners that seems like genuinely useful data that someone should be collecting. Drives me mad that so much of this stuff just gets shared as anecdotes and nobody ever tries to actually do anything systematic with it.