Oh, I will absolutely support that on my strfry relay.
Does strfry have the concept of public writes but authenticated downloads? Nostr.bitpunk.fm uses nostr rs and I have authenticated writes. Which means people can't send me messages unless I white-list them. Bur amethyst says your inbox should allow any writes on authenticated downloads and I don't know what that means.
No. As far as I know with it's base implementation, strfry does not have auth. What that means is that if it's a public inbox, anyone should be allowed to write to it, but only you can pull posts from it. Whether it's a DM inbox or a public inbox that deals with comments and likes and what not.