Does this guidance also apply to video game virtual currencies as well? My initial assumption was that "convertible" means it only applies to currencies that can be exchanged back and forth with fiat currency, but I don't explicitly see that stated.
In the case of Diablo III, you can sell your in-game virtual gold for real money in their Real Money Auction House, via PayPal. Other games have less official means of exchanging between currencies, but that's at least one official/built-in version that I can think of.
Blizzard and gold selling sites are considered MSBs, but not users.