Browser extensions are pretty insecure things. I'd recommend instead just creating a bookmark and have the url be the following:

javascript:(function(){location.assign("http://" + ((location.hostname == "www.palnet.io") ? "steemit.com" : "www.palnet.io") + ((location.pathname.split("/")[1].indexOf("@") == -1) ? location.pathname : ("/" + location.pathname.split("/")[1])))})();

That will do the same thing without installing anything.