Hello,
I pointed out some issues in the spec defined block-quotes a while back, see https://github.com/commonmark/CommonMark/issues/460.
And also proposed some changes to make them less ambiguous, and clear up written v.s. interpreted indentation discrepancies too. See https://github.com/commonmark/CommonMark/pull/466.
There was a little bit of discussion on the details of the particular fix, and also some alternative ideas on how to approach it. I wanted to see if I could gauge a bit more consensus on what to do to move forward by posting here.
Thanks for taking a look!