I can see from previous forum posts that Shift+Delete used to be available for quick deletion of a thought in earlier versions but has been deactivated.
Deletion of single thoughts
It seems unnecessary that experienced users should have to confirm each time before deleting even a single thought, particularly as we have an effective Undo function. Naturally, confirmation before deletion should be the default, but when faced with having to delete a number of single thoughts in succession we should be able to do it in one step and get on with our work.
Deletion of multiple thoughts from selection box
Here, one may prefer to enable confirmation, though since Undo is capable of reversing a multiple deletion, an experienced user might also appreciate the option to carry this out without confirmation.
In the absence of a more permanent method of hiding thoughts (such as tagging them) that does not depend on the Reports filter not being used for anything else, I find Forgetting too valuable to be used as an intermediate Recycle Bin. I Forget thoughts in order to hide them, not to store them temporarily pending deletion.
For this reason I would also like the option of making Delete the default rather than Forget, so that by pressing Del, maybe with a time delay of two seconds, the thought is deleted. Even Windows, lacking PB's Undo feature for deleted items, still provides the option to delete without confirmation.
My impression is that the decision to disable Shift+Delete was taken to protect users from themselves. However, a suitably placarded warning for the option should be sufficient to protect the developers from being sued for data loss.