Alright, so I'm unsure now about the rules concerning the Glitchless% Category. In the General Game Rules it is written: "Your run must be performed as if you started from a clean save file. You are not allowed to take advantage of anything that is unlocked after having already played the game, unless explicitly allowed by the category rules." Here's the thing: I was watching a run (specifically the current 3rd place) and there was at least 1 fire alarm pulled and there was at least one chess piece collected (the Kasparov Computer was on), but the player (as far as I'm aware at least) did not take advantage of any collectables. Does that mean we don't have to wipe the file if we want to keep the in-game achievements as long as we don't use them? Or is this an oversight? I apologize if I'm annoying anyone by asking another question about the rules.

Thats correct. You don't have to clear the file to run the Glitchless Category. Always ask if something is unclear :)

As long as you don't use any benefit that would be gained from collectables, you're fine. That's what we mean by "as if you started from a clean save file".