@gray It's a firewall that attempts to discourage AI crawling and other assorted Denials of Service by hiding most websites behind a JavaScript proof-of-work challenge like anything behind Cloudflare or the Kiwi Farms does nowadays.
As someone whose git instance got bombarded by crawlers so hard it eventually stopped working I added it because it was less absolute than dropping an entire IPv4 /8, and ever since the AI slurping either stopped or slowed down to a level that it doesn't make the server give up on serving anything. Crawlers are super annoying especially the ones that don't respect any time, resource or crawling restraints