That answered a question for me. I just kegged a porter and put a layer of CO2 on the top. I obviously overdid it and just a small amount of beer came out of the post. It was just a small amount so after reading this I'm not concerned.
A brew or two ago i had a massive brain fart being a lazy ******* and hit the preassure release on regulator on a burst carbed keg after dialing back the regulator. I had a healthy fill on that keg and i had nice foamy preassure release valve on first squirt !
So yeah one way valve and cleaned out regulator...