[MGlitch]

Originally Posted by Rev. Bob

Utter nonsense.

Yes, what you're espousing is utter nonsense.
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The more correct example would be the Kobo app forcing images to grayscale despite running on a device with a color screen. There’s no technical justification for the behavior, and it improperly violates the author’s intent.
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And it would still be a deficiency especially if done intentionally. Not a bug. You really might want to spend some time learning what constitutes a bug versus a deficiency.

Go read the RFC. Compare item three (“should”) with item five (“may”). Guess where you’ll find “optional” defined?

”Should” explicitly does not mean “optional.” The definitions are quite clear.

And yet it was your words I was quoting with "optional", not the technical specs. It's adorable how much you want to quote technical specs and yet ignore them as well.

1. MUST This word, or the terms "REQUIRED" or "SHALL", mean that the
definition is an absolute requirement of the specification.

2. MUST NOT This phrase, or the phrase "SHALL NOT", mean that the
definition is an absolute prohibition of the specification.

3. SHOULD This word, or the adjective "RECOMMENDED", mean that there
may exist valid reasons in particular circumstances to ignore a
particular item, but the full implications must be understood and
carefully weighed before choosing a different course.

4. SHOULD NOT This phrase, or the phrase "NOT RECOMMENDED" mean that
there may exist valid reasons in particular circumstances when the
particular behavior is acceptable or even useful, but the full
implications should be understood and the case carefully weighed
before implementing any behavior described with this label.

5. MAY This word, or the adjective "OPTIONAL", mean that an item is
truly optional. One vendor may choose to include the item because a
particular marketplace requires it or because the vendor feels that
it enhances the product while another vendor may omit the same item.
An implementation which does not include a particular option MUST be
prepared to interoperate with another implementation which does
include the option, though perhaps with reduced functionality. In the
same vein an implementation which does include a particular option
MUST be prepared to interoperate with another implementation which
does not include the option (except, of course, for the feature the
option provides.)

Neither "may" nor "should" is defined as "must" or "required", both are specifically stated to not be those, which the mere inclusion of terms like "must" would tell anyone with a modicum of common sense. You can argue levels of "suggested" but it is still never going to reach "required" unless you want to travel to an alternate universe with different rules, or rewrite the rules to your liking. However as it stands your guidelines are not supporting your claim.

The rules of English can be bent quite far, but even these guidelines stay well within them. It is you who are trying to impose an entirely different meaning upon the terms, even such as they are defined here, to try and defend your incorrect stance.