It is slightly confusing that when you change your preferences and refresh your watchlist, that these changed preferences do not take effect. This is because your previous settings are reflected in the URL, and these take preference over the defaults.

It might be a good idea to track the integrity of the previously used defaults, and inform the user when a 'conflict' is detected.

"Your preferences have changed since you last visited. Would you like to reload this page with your new preferences?"

Would required some sort of edittimestamp being passed in the url params or something and conflict detection. Might be a good idea to apply this somewhat wider into the core of the preferences, as with the increase in dynamic content, this might start popping up in other areas with dynamic/single page logic too.