This will be part of a new fun feature we're going to implement soon. We're just testing it at the moment.
It doesn't have anything to do with money, currencies, coins, payments, patreon, charging people for something, premium memberships, etc. It's going to be a new forum feature for everyone to use.
And the CHARGE tag itself might not be used at all. It's just here because I can't figure out how to remove it without breaking the entire add-on.
There's no point in discussing this further until the new feature is announced, so I'm going to lock the thread now. It's a few days away now.