Do you mean Choose Item Specifics or Custom Item Specifics? Because there doesn't seem to be any rhyme or reason to the latter; different boxes will show up at different times even when using Create Similar; sometimes an eBay recommended specific will show up as a custom one. I just figured it was eBay being glitchy (Item Specifics is one of the areas they keep monkeying with).
When you block a person, they can no longer invite you to a private message or post to your profile wall. Replies and comments they make will be collapsed/hidden by default. Finally, you'll never receive email notifications about content they create or likes they designate for your content.
Note: if you proceed, you will no longer be following .