Given the US recently made a bid to fast-track multiple censorship bills, KOSA included, and is also trying to kill Section 230 now, which will pose an existential threat to Fediverse instances hosted over the clearnet, how feasible would it be to host said instances over Tor/I2P?
Why is it the first time I hear of this?
Ah, because it’s apparently a fresh proposal, perhaps from Mastodon themselves.
https://www.w3.org/wiki/ActivityPub/Primer/Authentication_Authorization mentions HTTP signatures since the very first version of the document in 2017. The current efforts seem more in the direction of describing standardizing the existing usage.