Cloudflare doesn't block them, Archive.is intentionally refuses to resolve DNS queries from 1.1.1.1 due to lack of geo information. See explanation here: https://jarv.is/notes/cloudflare-dns-archive-is-blocked/

It doesn't/its complicated.

You can read about their reasoning here: https://news.ycombinator.com/item?id=19828702

Posted by https://news.ycombinator.com/user?id=eastdakota, whose profile reads:

> A little bit geek, wonk, and nerd. Repeat entrepreneur, recovering lawyer and former ski instructor. CEO & co-founder of CloudFlare. [ my public key: https://keybase.io/eastdakota; my proof: https://keybase.io/eastdakota/sigs/_uDY0ZsLTEWaNu5daRtuwzZtJ... ]