Are you sure? Someone broke into a Hetzner data center and a Linode one, physically intercepted the Ethernet cables for jabber.ru, and got certificates signed on their behalf.
dear sockpuppet =) I think the above commenter meant illegal physical access. The jabber.ru MitM situation was likely carried out by a cybercrime unit of the German police forces with a court order... and this is the adversary most people forget about.
Lesson to learn: Let's Encrypt does not protect against MitM by a state-level actor, unless you take precautions.
*let's assume network admins won't MitM your server for personal vengeance reasons
https://notes.valdikss.org.ru/jabber.ru-mitm/
https://news.ycombinator.com/item?id=37961166