Actually, nothing in what you quoted supports your thread title. He said that he no longer believe that didymo spread is the major threat, but nothing that you quoted indicates he no longer believes that didymo is not spread by felt soles and other angler's clothing. Rather, he said that the didymo has largely been spread already, and now it's just a matter of stream conditions which determine how active it is. Maybe there's something else in the article that supports the title (I haven't read it), but what you quoted does not.