Unapproved deals

You are correct.
Any deals made that involve anything to do with trading In-game items/money for either paypal or any sort of irl currency is not permitted anywhere on the server and will lead to a severity 3 punishment. You are strictly only allowed to make trades within the MCC store. So exactly as you said, you aren't allowed to trade spawners & other items for paypal / irl currency it must ONLY be buycraft. Buying gift cards rather than trading with real money is the accepted way of making a trade.

I'm not exactly sure this rule was added although I can assume it ensures that this way all the funds made via trades will stay within the server ensuring that people are no longer able to self benefit off of the server no longer making their own personal funds. The rule has been implemented for quite some time now. I remember back in the day when IRL deals where a huge hit as I know many people who made huge amounts of money, although unfortunately now thats not permitted.​

 

Lewklo covered everything you need to know about the punishment itself above. Regarding the blacklist, if you do an IRL deal and chargeback, then it is blacklistable. Meaning you used PayPal to get something and then charged back after the deal was completed(something in the BC store). This would result in you getting blacklisted, or the person who did it, getting blacklisted.