>HTTPS + HSTS would prevent the author from spoofing the DNS of that those sites and sending them to a server over HTTP thus avoiding the certificate errors.
I'm confused, how would that help? Could the attacker (the author, in this case) not get a valid https certificate for these domains, returning spoofed DNS responses when the CA goes to validate it?
yes, but HTTPS + HSTS would not enforce a certain validation level, eg you can't enforce EV certs only in HSTS (as far as I know), so a DV cert would be sufficient
I'm confused, how would that help? Could the attacker (the author, in this case) not get a valid https certificate for these domains, returning spoofed DNS responses when the CA goes to validate it?