Explanation of how the player movement code in Quake gives rise to these three different player movement "bugs", with a quick look at TAS movement mechanics at the end.

Big thanks to the Quake Speedrunning Discord for helping me out with getting TASQuake running on my machine, and for clarifying terminology.

Here are the original C versions of the acceleration functions:
https://github.com/id-Software/Quake/blob/master/WinQuake/sv_user.c#L190