What it does
Contact with a wall restores actions you had already spent, so a wall is not the end of a movement — it is the middle of one. Chained properly it turns the vertical geometry of a map into a route, which is why GunZ maps are read as three-dimensional in a way most shooters of its era are not.
Why it exists in the code
Hitting a wall resets part of the character's airborne state, and that reset was never gated behind a cooldown. Every map in the game was built and played with this behaviour present, so removing it would not be a fix — it would be a different set of maps.
This behaviour is preserved deliberately. It is not on a list of things to fix.
The mistake everyone makes first
Aiming at the wall instead of past it. The contact is what matters, not the collision; drifting into the surface kills your speed, while clipping it on the way somewhere keeps everything you had.