Exclamation marks in links

[Lastwebpage]

Hello,
we have a wiki (mediawiki) and SMF forum (1.1.14).
The wiki contain a few sites like www.example.com/blahblah!
If I post this link in the forum I get www.example.com/blahblah! the exclamation mark is not part of the URL.

What's the problem? If I interpret http://www.faqs.org/rfcs/rfc1738.html correct ! is a valid charater.

As a workaround I created wiki redirects from .../blahblah to /blahblah! it works, but what's the reason?

Peter