Now when the extension works perfectly, I would like to suggest one important feature: tooltip text column.
It should be straightforward: one additional column in database and the admin menu, where you can put the description what is hidden under the link and what will be displayed when you hover over the link.
I understand now.
You want to use this extension to produce links to other forums of your board.
This extension is rather meant to produce external links on technical terms.
It would be rather difficult to modify it.
Have a look in the code, if you want.