The reason things might be confusing is because the gray bars you see in wider lists are actually just the left border - a clever way to have a bar next to list items. So there are two ways,
- using the 'border-left' rule or
- using the 'list-style' rule
if you use them both, you would see the bar then the list-stle you chose
The other issue is that not all plugins use the same 'classes'. If I create a plugin with a widget and it makes a list using a class of 'jd-list-item' and someone else creates a plugin/widget/list with a class of 'fubar-list' then the CSS you would need to style my list would be different from the other list. One set of CSS would not apply to both.
Now if you can think of a way for everyone to use the same class names...hmmm...you could call it something like...standards. And then maybe we could get all the browsers to treat it all the same way...