And this is where I can tell you it’s user error!
Apparently when I was testing block and unblock back when I set up the server, I managed to leave threads.net blocked.
I unblocked it, and now I can follow a user in the web interface via @user@threads.net, but not by their profile URL, which I guess is a peculiarity of Threads that it doesn’t return any actor information from that URL.
Thanks for checking in on this, and for, you know, building the thing!
#