One thing we're looking into at Mutiny is a way to do multiple pubkey locked ecash notes. I think someone could create the an ecash contract that goes to two outputs, one to the service and one to the recipient. If you had a lightning invoice be the funding of that, then it's effectively a payment split.

I've been saying this for awhile, but I think ecash is a way better experience for something like Stacker News. And with fedimint federations, whether SN is a member or not, it's a much more favorable position to be in.