I have an inkling of what you're talking about.
First, the triple jump: by rejumping really quickly after jumping once, you do another regular jump, from witch point you can go higher than usual by doing an actual double jump.
Only thing is, if I spam fast enough, it seems i can go arbitrarily high, but it's way too inconsistant for me to do anything useful with it or figure anything out about it.
Second: the glitchy walljump (named after the glitchy wallkick in Super Mario 64 which has got a similar effect). I seems that, sometimes, when walljumping while going off a wall (say by holding the other direction or simply reaching the height of the celling below), you can walljump without the opposite momentum that normally comes with a walljump.This can save a surprising amount of time when skipping the section to activate the giant windmill. I would know since I've done it accidentally on a couple of occasions.
My best guess is that you can still walljump one physics frame after going off a wall, but the game doesn't see any wall to send you backwards from, so it just doesn't.
Bonus observation: it's possible to slide off a wall without being in contact with it by holding the opposite direction for juuussstt the right amount of time. However, walljumping from this state sends you back like normal.
Finally, backwards stair climbing: with the sliding walljump, it's just barely possible to climb upside down stairs, which you could potentially use to skip the oscillating platform, saving heaps of time.
I've not done this yet as it is incredibly difficult, but i'm trying.
