Nice plugin! Just spotted a couple of things I wanted to tweak, mainly the logic of the ternary statements, such as:
return (($this.is('ul, ol')) ? true : false);
Here you're checking the value of $(this).is('ul, ol') which returns true or false, so no need to return T/F based on the result of it, you can just return it :)
This happened on about 3 occasions, edited them all and tested it, seems to still be fine.
Tidying up some of the ifs