yes, you can tell where enemies are in fog of war

Hmm, well I wouldn't permaban people for using a known... built in setting, even if it gives an unfair advantage.

_edit_

To whoever downvoted me later - I would consider it a bug if it was user settable without cheats. Similarly you could see trough smokes in CS for a long time by changing some video settings. You don't (usually) ban people for bugs.

it was restricted, you couldn't force it without cheats

Ah, yeah sounds plausible then. I somehow don't buy the guard page/hw breakpoint explanations. This also lines up with "[information] that wasn't visible during normal gameplay".

Yeah if you ran with the software renderer in Counter-Strike I think the smoke grenade's smoke didn't work properly.