Hmmmm.... It seems to be a bit flaky but I was able to do the following:
1 ) In the email notification I get, click on the "View all results" to load the list of searched items.
2 ) Click on "refine your search" link near the top of the ebay page.
3 ) Click on "Seller", then check "Only show items from", "Specific sellers", select Exclude, add in mikedenero.
4 ) Click Apply.
Then I think the following is the key in order for it to "stick".
5 ) Click on "Follow this search" link near the top as it will create a new search.
6 ) Go back to your email notification and click on "Refine this search". You will see the new search (it may appear as duplicate search of the previous one, so may have to figure out which is which).
7 ) Then run one of the searches and check if your change is there (you'll have to "Refine your search" again once inside).
8 ) If the change is
not there, back button out to you get back to your search list and Unfollow the search (under "more options" for that search).
9 ) If the change
is there, back button out and unfollow the other search.
There may be an easier way, but it didn't seem that just modifying the existing one actually stuck. But with the above method, I am no longer seeing items from mikedenero.
Of course, knowing ebay, this will probably only work for the next 12 hours. Then they will make a change and "all bets are off".