Have a look at this

http://seablick.com/blog/articletype/articleview/articleid/91/dnn-url-rewriter-on-steroids.aspx

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The article that albert kindly linked to points you to the Friendly Url Provider that I have authored.  While it's a very useful product, it won't get you what you are looking for.  You actually need to replace the entire Url as you have suggested.

I have another product that allows you to replace the Url for any DNN page (as well as doing a lot of other things with Url Rewriting).   You can certainly replace  "S%c3%a9journer" with "Sejourner".   You can find the product page here : Url Master Friendly Url Rewriter for DNN

Using an IIS rewriting solution isn't the right way to go because it won't generate the correct Urls in your internal links and menu items. To do this, you need an inbuilt DNN solution.

Fee free to contact me if you have any questions