Consecutive lists are merged into a single list in CommonMark Markdown 1.2

When rendering two consecutive lists to markdown/1.2, they are separated by an empty line but use the same list marker, and CommonMark considers them as a single list (an empty line between list items only makes the list loose). Thus they're read back as a single list.

Example: render the following xhtml/1.0 content to markdown/1.2 and parse the result back:

<ul><li>a</li></ul><ul><li></li></ul>

The result is

* a

* 

which is read back as one list with 2 items instead of 2 lists.

A possible fix is to alternate the list marker (e.g. "*" then "-", or "." then ")" for ordered lists) or to separate the lists with an HTML comment.