What would a glitchless run entail? Are we talking no zoops (for co-op)? No infinite wall jumps? No neo-climbing? Would it be just a more limited NMS run?
On a somewhat related note, solo runs have been split up into any%, NMS, & RMS categories to mirror the co-op rules. This way, NMS stays in bounds and RMS allows for out of bounds, with the general definition of "in bounds" still being any place you can get to with autograb on and without using unnatural techniques like infinite wall jumps and neo-climbing.
Some examples of out of bounds stuff: climbing up and over black webbing, climbing up and over invisible walls, climbing up the wall to skip the fire maze in Ch 5, climbing up the left wall in the steam pipe room in Ch 5 to skip the cutscene before dropping down through the grate.