What would be interesting is if different discourse instances can inform other discourse instances that a link was used.
This is similar to the linkback protocol, but restricted to a whitelist and to discourse instances only. This should minimise bad actors spamming other discourse instances.
This would allow for cross forum collaboration, with not as much technical hurdle compared to actually sharing topics and user accounts between discourse instances:
Perhaps to minimise whitelist overheads, you could request discourse.org to send you a whitelist for the most popular discourse sites out there. Then manually add in the smaller discourse instances that your community talks to.