On saturday I was able to receive a certificate from comodo depsite the
subdomain having a CAA record only allowing Let's Encrypt as the CA.
Here's the cert:
I have by now heard from multiple other people that confirmed the same.
Seems right now Comodo isn't checking CAA at all. There's also a bug in
the Mozilla bug tracker:
I was originally informed about the lack of CAA checking at Comodo by
Michael Kliewe from the mail provider mail.de. However that was before
CAA became mandatory. But even back then the Comodo webpage claimed that
Comodo would check CAA since at least 12 months:
I have covered this also today in a news article for Golem.de 
dev-security-policy mailing list