I think this is the (only) place in the Nginx docs that mentions 444: https://nginx.org/en/docs/http/ngx_http_rewrite_module.html#return https://nginx.org/en/do

I think this is the (only) place in the Nginx docs that mentions 444: https://nginx.org/en/docs/http/ngx_http_rewrite_module.html#return https://nginx.org/en/docs/http/ngx_http_rewrite_module.html#...