> LE is still useless for UGC sites with per-user subdomains

Let's Encrypt is a public service, aimed at operators of individual systems who host web content or email in a casual sense, were poorly served by the complexity of getting and maintaining a TLS cert, and who empirically were basically not doing TLS.

Your posited blog host is going to be a professional or semi-professional web admin. Just call up Comodo or whoever. There's a product for that need. Let's Encrypt is not it.

In the vernacular: cry me a river.