I tried enclosing the following url in the URL tag(using the button available below), but failed while submitting the post. The error keeps mentioning that there's an invalid html tag.
This is a really ugly workaround, but you can replace the characters that UBB complains about with the HTML character set equivalents, and get a working URL from it.
If you are not sure what I mean, try doing a quoted reply to my post by clicking on the icon at the top of my post. You will then be able to see exactly how I achieved this.