The service being credited should only be one that the seller is using within that particular listing. Listings that do not meet eBay's policy on third party credits may be ended.
eBay doesn't allow AuctionSniper logos to be placed directly into auctions. Some people still do it, but if eBay notices they will most likely pull your auction. The best thing to do is what Sniper Bill stated above.
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 .