Daniel LakensBoulder route difficulty ratings deserve more attention from the measurement community. The certainty with which my friends can agree a route is a 6B, but not a 6B+, is a marvel of validity and reliability in measurement of which I do not understand how it has been achieved.
Robbie Clark@lakens Agreed that it's generally pretty nuts how consistent ppl are. But grades differ massively depending on context. When people primarily climb in the same place, they get a sense of the grading and style there, and become good judges within that context. But put them somewhere unfamiliar, with a different setting style, or on a gradient/hold type they're weak on, and they're often terrible judges.