Take this HTML:
Parse to wikitext:
* asd sdf
Parse back to HTML:
I'm not sure what should happen here, but definitely not this.
It's rather easy to run into this in VisualEditor – take a paragraph with newlines and convert it to a list item. I ran into it making this edit: https://en.wikipedia.org/w/index.php?title=Polish_nationality_law&diff=prev&oldid=618961884 (I manually replaced the newlines with spaces before saving).
See Also: T55568: Automatically switch from wikitext to HTML syntax in serializer when attributes were added to elements