That he would accept the label of scammer should he not hold up his end of the bargain, that is, that he understands that not holding up his end of the bargain would in fact make him a scammer and justifiably labeled as such by the community. It reads as reinforcing the seriousness of the bet as an enforceable agreement such that violating it would constitute scamming.

I wish it wasn't so, but I do believe that Matthew, at least in the beginning, believed that Pirate was going to pay people back and had he won, would have gleefully accepted any funds paid to him and pursued scammer tags for anyone who didn't pay him back. If he didn't believe this, he faked it *incredibly* well.

By the way, if your implication was that it's a reasonable interpretation that accepting a scammer tag was somehow full payment for the bet, then how do you explain why other people kept betting or why people raised their bet amounts or asked for escrow? It's not like Matthew could get more than one scammer tag. So it's pretty clear that nobody accepting the bet, except possibly the first person or two, had this interpretation. (And it's silly and unreasonable.)