My apologies for being slow in replying to this thread, I did, however get back to Bob later in the same day he first contacted me about this issue.
I reminded him that I had set up a banning feature a long while back upon his request. This feature lets me ban a specific buyer from bidding on the auctions of a specific artist. When they try, they receive a message that the artist, not DPW, has banned them.
In most cases, simply flagging a nonpaying bidder is sufficient and more polite. The only reason I can imagine for banning someone is if you know before they can be flagged that you don’t want them bidding on your auctions.