How good is VAC?

If they hack they will be found out by Vac eventually, VAC is not instant that like to do ban waves.

Block him on Steam.

I dont think dark souls uses vac.

how about reading Valves Vac Information Site?
Reports arent even accepted nor do they increase the speed of getting a guy banned. Only Vac bans

Also, make your comments friends only and you won't be harassed by randoms from mp games.

VAC is shit, cause volvo do not update it regularly. And this is sad.

You can also just delete the comments from your profile. You have the control.

One thing you need to remember about VAC is that, after it detects someone hacking, it waits a random duration before it bans the person. This is intentional, as in removes the possibility of one person getting banned because VAC has learned to detect his current hack and warning all his hacking friends before they log in. So his friends log in with the same hack, and they all get caught.