It is quite easy to create two adjacent lists that appear to be one list (but for a small amount of extra spacing) through copy/paste or deletion. More often than not this is not what the user means semantically, so such a situation should be highlighted to the user and they should be given an easy way to fixup the code.

I have yet to see an editor which does this well, but that shouldn't stop us being the first.

Steps to reproduce

Just as a helpful example.

1. Create a list.
2. Decide to end the list by pressing enter while on a blank bullet.
3. Change your mind and decide to continue the list by clicking the list buttons.
4. Now the document has two separate lists, but your mental model only has one.