I do not understand when we are suppose to say You or y'all or You all and when we are not. I assumed there was an attempt to get you to realize when the command was singular or plural but now it just seems to be frustratingly capricious. Sorry, I know this is a rant and not a discussion topic but hopefully somebody with editing access reads this. I hate this topic for this reason and this reason only.

don't come in - also proper answer

Is this the way that it would be written on a "do not enter" traffic sign?

Where do i find a source for the prefixes used in negative commands? Any help or suggestions are appreciated!