> larger orgs currently building on Matrix would feel victim of a rug-pull or a bait & switch

Fair. The bait and switch could be avoided by grandfathering in current orgs. A more hands-off, related idea is that you could come up with an unenforced, suggested payment. Essentially consider what an ideal economically sustainable licensing system would look like, and publish that as a suggested donation.

> We've always aimed to avoid Matrix being pay-to-play (e.g. eschewing tokenisation schemes).

I agree with eschewing pay-to-play or plopping some half-assed crypto grift on top (or what some would call a "tokenization scheme"). I would dispute characterizing my suggestion as pay-to-play, as payment wouldn't be required to use the system. It should be totally up to the user how much to set their bounty at, including zero if they're willing to accept the greater amount of spam (or wish to use some other spam filtering method). The idea here isn't for anybody to make any money off of getting messages (the money would just be returned if the receiver accepted the message as non-spam), it's just to make large scale spammers lose money.

> Instead, the angle we've taken has been to let users publish and subscribe to reputation feeds (a bit like email DNSBLs, but more transparent and less of a shakedown) in order to empower users to block stuff they don't want to see.

That makes sense as a feature generally, although I think its solving for a different sort of problem. The blocklist seems like it would work best for allowing users to cultivate a particular culture (i.e. subscribe to a blocklist for those who use excessive profanity, or talk about certain undesired topics, etc.). But a "Nigerian prince" style spammer can make new accounts and blast out messages faster than you can identify and add them to a blocklist. However if it on-average costs that spammer $2 per message that they're unlikely to get back, it suddenly becomes prohibitively expensive to engage in that type of behavior.

> But perhaps one could combine the two ideas: you could have a personal rep list which users pay to be on, and you get the payment if they turn out to be spammers - similar to systems like https://www.bbc.com/worklife/article/20181023-people-pay-20-....

Hmm, that's an interesting modification. I'll need to chew more on the incentives. I would say the approach in that article is closer to my original suggestion, except instead of the money actually going to charity it would just go back to the sender once the author replied to their message.

> Much like email, i'm not sure these semantics should be baked into the protocol itself. (But the infrastructure to support it could be - thus MSC2313: https://github.com/matrix-org/matrix-spec-proposals/blob/msc...)

When I look at that proposal, it seems to me like it's "baked into the protocol itself" insofar as its proposing how to use existing room primitives (namely state events) to implement the concept.