Per usual, excellent job. I would offer you a chef's kiss emoji (get it) if I could, especially for your rad creation. Thanks for the patience too – juggling this along with the 6.0 release has made it so that it takes me a bit longer to reply to feedback.

It seemed impossible to add a new item to the top level after an inserted sub-list. Clicking the first item and hitting Enter deleted everything nested below it. No amount of clicking or keyboard input seemed to get me back to the top level to continue adding more items.

This was due to a fun bug that has since been fixed: https://github.com/WordPress/gutenberg/issues/40767 Like you, I found myself quite confused by the keyboard experience and found it did the opposite of what I expected. Expect this to be a better experience in 13.3.

It also seems impossible to escape the List and into a new Paragraph block. In the past, this could be accomplished by hitting the Enter key twice while on the final list item. That action now creates a nested list.

This is definitely a recurring point of feedback. I’ve noted it in a related issue here (might need to split these out depending): https://github.com/WordPress/gutenberg/issues/40769#issuecomment-1122867474

Markdown-based lists are also not transformed into a List block when pasted into the editor. The formatting is lost, and each item gets absorbed into a Paragraph block.

Excellent find. Opened an issue here: https://github.com/WordPress/gutenberg/issues/40980

One enhancement I would like to see for Quote v2 is the element separated into a standalone block. This would allow end-users to customize its design separately from the wrapping on the block and global levels.

Agreed. Having the citation block as an inner block has been discussed here along with whether it should just be an item in the toolbar to add a citation: https://github.com/WordPress/gutenberg/issues/15486 I’ll note this in my write up for now as this discussion and work evolves.

Currently, only theme authors can modify its style, which must be handled via custom CSS.

Some talk around adding theme.json support for modification too just as a proactive, fun note: https://github.com/WordPress/gutenberg/issues/35735