ZDoom

Technically [Not a bug] then. Whatever fixes to the bounce logic would technically be a separate issue

Internally nothing is ever done with the return result against planes which is the real issue. Currently I'm working on cleaning up the bounce code in my own Actor class and want to do a sweeping physics update to them later on down the road. There's tons of things broken with the logic like how it straight up doesn't even recognize that 3D floors exist (which leads to the infamous 3D ramp bug where projectiles get caught trying to bounce on them).

Judging by the structure and implied logic, it seems that returning 0 in [url=https://github.com/ZDoom/gzdoom/blob/22203cbc1a9935a03b0d2747a4e76396821f8691/wadsrc/static/zscript/actors/actor.zs#L547]SpecialBounceHit[/url] should result in the projectile stopping and exploding. However, that's only true for lines and actors. If the projectile hits a secplane, returning 0 makes it slide along the plane, exactly the same way as returning 1 does. (Tested in 4.11.3)

That seems like an oversight.