It’s clear that any kind of feature that allows members of a forum to reward each other financially needs careful design and protections from fraud. It’s almost essential for Discourse to help manage the financial back end and fraud prevention, so I would expect some percentage of each financial transaction to go to Discourse, some percentage to the forum itself, and the rest to the intended target of the contribution.
The most important fraud use case to consider is that a gang of hackers can show up, create 100 fake accounts, and start sending tokens / contributions to each other. They use stolen credit cards and their hope is to cash out in 30 days, when the reports of a stolen credit card might not start coming in for 60 to 120 days. One way to deal with that might be to have “trust levels” and by default users can only cash out after 180 days, which should catch 95%+ of the fraudulent credit card use.