I like the idea of others following, observing, favoring and commenting on my lists. But I don't want anyone adding to my own lists, except their own comments. I would have no problem with someone copying my list, making it their own, and THEN adding to it as their own list. But there is no reason anyone should add anything to my list, but me. Otherwise it's not my list. It becomes everyone's list and that's not my purpose.
I do welcome comments on my lists. They help expand my knowledge of the area.