I just read through the incident report and noticed these three lines:
2020-02-29 03:08 UTC: Let’s Encrypt engineer confirms bug.
2020-02-29 03:10 UTC: Let’s Encrypt SRE team disables issuance.
2020-02-29 05:22 UTC: Fixed version of Boulder is deployed (containing https://github.com/letsencrypt/boulder/pull/4690). Issuance is re-enabled.
This is an absolutely amazing response time for both disabling issuance, and fixing/testing/re-enabling.
I know this is a stressful and frustrating situation, and many end-users are expectedly upset, but the emergency performance of the LetsEncrypt staff here is simply amazing and deserves commendation.