Instead of using a user-supplied title, whenever someone includes a URL in your forum, the external page is retrieved, and the title is used to link to the page. A link to google would read
Whenever there is an interstitial page, a countdown for 5 seconds will start before the user is actually redirected to that page.
Whenever a link is posted, a snapshot for the external page is generated. When the users hover over the link, the snapshot will be shown.