If you delete "...\Half-Life\valve\cl_dlls\particleman.dll" in the game smoke disappears
Can you embed this library in client.dll?
It will still be easy to patch. Also it is easy to check for abuse.
It is not a bug but a standard proper placement. Players can manage their sprites also and make different gameplay mods.
There should be a way to not remove smoke in game. It's a bug/cheat.
Its an exploit i already reported in #2058