Funny thread there on steampowered but there are 83 pages of talking and nobody actually made any research as far as i know.
If this is a game issue it would be only on one of the games (cs1.6 OR css OR csp) and csp is most likelly to NOT have this issue as the recoil code is 100% customcoded and diffirent than 1.6 OR css.
It could be (as they say in your steampowered thred) a hardware issue but it would appear just in one of the games and the odds are reaaaaaly small for such a thing to happen. If it is hardware then I'd blame the CPU instructions (i.e. mmx, sse etc.).
Again IF this issue is true then NOT having the horizontal recoil is the problem, not the other way around.
The good old 1.6 is working diffirent on dual/singlecore cpus, it works (shoots, moves etc.) slower on fps other than 100 and the wall shot decals are as far as i know CLIENTSIDED which means that even if you manage to find a pattern to follow to get the no-horizontal-recoil thingy you will not gain any advantage.
In short, 1.6 is full of bugs and it works best on constant 100 fps.
This sharp screen shaking was the most annoying thing in 1.6 since it came out. I loved how it was smooth in 1.5.