Anticipating resentment of my taking too much space in Q&A. here is a second item
from The Vocabula Review archive, which I hope may elicit comment:
"3. doubt that Misused for doubt whether. " Although I never fail to sympathize with the general concern, I doubt that it's possible to engineer a
happy return to a world in which secrets could be kept."

USE doubt whether. [Harper's]

To me, "whether" always implies a comparison, a choice, and "whether or not" can be clumsy.

Please comment.