Ian got back to me by email.
It appears that removing this rewrite will effectively get rid of the main web-site menu around the forum.
That is the downside, that is: if you don't have other means of accessing the main site yourself.
The upsides from the forum point of view are:
- full url in the address bar
- topic title in the title bar
- way more reading space
I have created a small .js file that has the rewriting removed.
When you ise IE, it is very simple to replace when you use the rules editor of Fiddler2 (
http://www.fiddler2.com).
You get into the rules editor by pressing Ctrl+R inside Fiddler2.
Then add this rule extension to the OnBeforeRequest method :
if (oSession.url=="www.un4seen.com/un4seen.js")
{ oSession.url = "www.xs4all.nl/~jp/www.un4seen.com/un4seen-new.js "; }
Didn't want to keep that one for myself, so if you need it, here you have it

So now I can finally enjoy all the bookmarks inside my external bookmark repository

--jeroen