If you want to remove ebay results you can tick the box, the search box only looks at the product name so -ebay won't do anything. Is it only the ebay example you were considering, or do you think it has a wider benefit?On filtering: would you consider adding negative values as used on other search engines? e.g. "-ebay" to drop all ebay entries from the search.
On display: I'd prefer to see a black font used for the list. Even though I'm not colour blind, I find the red difficult to read.
Here's a black link example, not that I'm convinced to change it, I will take the feedback onboard but I quite like the aesthetic.