I think this idea is really cool, I just don't see myself using this due to the alternatives (GitHub pages, static blog generators etc.)
No, GitHub pages are tied to "an" account. It can be a secondary "anonymous" account. You can create an anonymous bear blog or one of the other million free writing and zero maintenance tools. It's certainly more anonymous than having to disclose your real identity via a credit card on a random person's page.
Also, what sort of content do you hope that your target audience (Bob the landscaper who is non technical but has a super urgent desire to send a message to the world in an anonymous way) will publish?