At the top of your listing, where it says "Ebay Site" (normally it says United States or whatever your default is) you have to change it to "Ebay Motors" and then the categories should pull up.
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.
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