Non-spaced indented entirely automatically numbered lists do not render, and spaced lists do not render correct subsequent line spacing

2

As pointed out on GitHub, this is intended behavior, which has very good reasons. If CommonMark changes its behavior to work as you use it, it would break for the far more common way it is used.

Also, there is an easy solution for your usage. For autonumbered lists, use all 1s rather than 0s:

1. Placeholder
   1. Placeholder
   1. Placeholder
   1. Placeholder
   1. Placeholder
1. Placeholder
   1. Placeholder
1. Placeholder
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