Currently there is a way to leave some parameters intact. There really needs to be a way to customize that feature.
It is fairly simple to clean up parameters you know about after a cookie has been set, but sometimes you can't set a cookie thus you want the parameter intact.
Also there is a reason to use ? parameters rather than '#' fragments because it is much easier to use the data within code on the page for various kinds of segmentation.
I realise you could use Jquery to set hidden parameters within a subscription form, but that can be less reliable.
Also parameters are more likely to be retained across browser sessions from bookmarks and forwarded links.