I made some changes to #tagspub over the last couple of days. It's now using the #IFTAS DNI and AUD domain blocking lists, both for sending and receiving data. It will not let actors on those domains subscribe to tags, send activities, or read any data from the site. I've tried to harden the service to blocked domains as best as I could, which might have been too tight -- let me know if you have problems receiving data from the service.
This is defence in depth -- we still use block-respecting boosts, so if your blocklist goes beyond what's in the IFTAS lists, users on those domains still won't be able to read your content. But it doesn't work the other way; #tagspub will always block those domains, even if your server is more lenient.
Inspired by your recommendations to folks to look at the public tag feeds on different servers to understand how much tags do, or don't federate, I've been building a little site to help do just that.
Here's a screenshot of the current state, still needs a lot of work (esp. visually), but I'd welcome feedback.
(I was going to try to get it more polished before requesting feedback, but it seems like I might as well do so now.)