I agree with a lot of the spirit of what they're saying, but I'm pretty sure I wouldn't agree with their concrete applications of it (although they are unclear in the thread).
I think blurring the lines between public and private spaces is the opposite of informing consent. Cultivating unrealistic expectations of "privacy" and control in what are ultimately public spaces is actually bad, imo.
Informed consent in the fediverse should look something like a message on the signup page that says: This is a publishing system. Be aware that everything you publish here will be distributed to a bunch of other servers which are not under the control of us, the operators of your server. When you edit or delete something you've published, we will honor it and relay the message, but other servers may or may not honor it. There are many other tools for private (encrypted) group communication, but that is not what this is. ActivityPub is for publishing.
ps: I, for one, am glad that the Internet Archive exists!