I like Dryopithecus's intention, after all anything's better than not being able to use the keyboard at all to delete links!
But I don't see why we need a keyboard accelerator at all. It would be far simpler to have a Thought context menu option, saying "Delete link with Active Thought". PB must be able to tell if any thought visible in the Plex is linked to the Active Thought or not. If we had to use a keyboard accelerator, you'd have to use both the keyboard and the mouse, just to delete a link! I also disagree with Steeph, there's no risk of losing a link if you accidentally delete it; Undo will get it back for you. This issue doesn't bother me right now as I like my little macro; all I have to do is move the mouse cursor over the link to be cut, press Win+X, and - snip! This is a link-oriented, not a Thought-oriented, solution. I thought, we have Ctrl+Click to add a Thought to selection, so why not a key-enhanced click to cut a link? Haven't looked back since. Well, you know where to find my macros if you want it. What does annoy me is 5.5's new feature of not making highlighted links stand out from the rest by making them the same color as unhighlighted links. Let's hope they change their minds on that one.
PB 18.104.22.168 on Windows XP, J-1.6.0_17