I have heard and seen from clips that the smoke is not consistent at concealing, or so it seems. I wanted to make sure whether it actually is that way or not. I know that the server at least communicates the position of the smoke particle emitter objects, but I am not sure whether the behavior of the smoke is the same on every client the server communicates with. If only the smoke position is synchronized and the particle emitting is set to random per client, it would be the cause of the supposed problem. May that be the case, a fix would be to seed the smoke, so that it spawns the same on every client.
Another explanation would be that the smoke's effectiveness is very reliant on the particle effects settings. If it were the case that less particles of the same size are created, it would be possible to have a particle that would conceal on one client and be absent on the other. A possible fix could be to increase the particle size on lower settings.
I may be totally off, with everything I propose being the case already. In which case, I would like someone to tell me.