Someone once told me that walking under a ladder is bad luck. All sorts of opinions in the world.
The EPA hasn't allowed automakers to vent crankcase gases to the atomosphere since the 70's. Each one must ingest those gases back through the intake and some use a separator first to return the liquid parts back to the crankcase, as it keeps the stuff from building up in the intake system. If this was a bad thing, I think we would have figured that out by now. My separators drain back to the sump, as does the BMW in my driveway. All three have given great service with no signs of trouble. The general rule is that if it came from the engine and hasn't been contaminated with external influences, it is ok to put back in the engine. Most modern auto engines even send some of their own exhaust back into the engine (EGR).