[jl6]

I think “bug” used to be slang shorthand for the more professional term “defect”, and under that definition the Notepad change would accurately be described as a new feature.

But the word bug has been coopted by the masses to have the wider meaning of “doesn’t meet user expectations”.

[squiggleblaz]

"Defect" always seems like a johnny-come-lately polishing of the word "bug", rather than vice versa. I would be surprised if "defect" is truly the original term for a software bug, and "bug" was chosen as shorthand.

In any case, bugs need not be only in software. As as earlier comment says, bugs can be in specs, too. Here, the spec was buggy and that has been resolved.

Or to put it another way, the defect was in the spec, and that has been resolved.

(Note that many specs are implicit and best derived from the software in question. If that is the case for Notepad, then fixing the bug in the spec requires one to fix the code. I somewhat doubt Microsoft follows that practice, but it's certainly not beyond the realm of the possible.)