Create a product and give it a tag "test tag". Now visit that products page and click the "test tag" tag, the search results return nothing because space gets turned into %20 in the URL which doesn't get url decoded back for the query..
I imagine other special characters would also fail. Tags should be stripped of all special characters except only those legal as a tag in a url .
Again this is something I could have fixed for you if there was a git repo..
