there was a convar in the game for 6+ years that let you see particles in the fog of war; 99% of cheats forced this convar on. source lets you request CVars from the client and the value, so they simply did that.
to be clear, this was not a honeypot, but they claimed it to be
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.
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".
to be clear, this was not a honeypot, but they claimed it to be