What note(s) are a diminished 3rd above D-flat?

Question

In What is the interval between Db and D# some of the comments indicate that the interval Db->Eb can be considered as a diminished third. I would think that Fbb (double-flatted F) is a diminished third above Db.

Is there more than one (name for the) note that is a diminished 3rd above Db?

If so, wouldn't this ambiguity exist for all of the other intervals?

Note: I'm aware that in a world of equal temperament, this is kind of moot, but that formally there is a difference between Eb and Fbb.

Answer 1

There is exactly one note that is a diminished 3rd above Db: Fb.

Db to Eb is not a diminished third, it is a major second. Those comments are wrong. This question explains the difference between two enharmonically equivalent notes.