Paul, although I cannot fix the specific problem re: Technorati Watchlists, I can offer an alternative. All Technorati keyword, URL, and Tag search results are available as RSS directly from the search interface and support complex queries including language filtering.
An English language filtered query for "Paul Watson" -pirate -captain -whale looks like:
If you wanted to further filter for blogs with A little authority, could run that search and either use the feed auto-discovery or the Subscribe button.
I realize that you would have to unsubscribe and resubscribe each time you refine your search, but I do believe this solution will give you what you asked for as far as subscribed search results go.