Of course distortion is not in the definition. Amplification is
pure gain. Any deviation from pure gain is more than just
amplification.


Not by definition. You are simply trying to present your opinions on what an
amplifier should be by you your ideals as a definitive global statement on
what an amplifier is. That is wrong.

Rusty said


I agree all amps do deviate from ideal amplification. However,
amps can be designed such that deviations are well below the
threshold of hearing and even below the limits of available test
gear. For the purpose of amplifying audio signals they can be
considered ideal amplifiers ala "straight wire with gain".


Many things "can" happen. That doesn't mean they have.

Rusty said


I also agree a designer can intentionally add distortion and like
the result. Guitar amps would be a good example. In that case
it would not be a poor design but it's also not just an
amplifier.

If you know this then maybe you shouldn't make global claims of fact based on
your ideals.

Rusty said


I belive the job of an audio power amplifier (preamp input,
speaker output) is to amplify the incoming signal without adding
any audible effects other than pure gain.

Here you are on the right track. You are stating your ideals as your ideals.

Rusty said

To do anything else
changes the intent of the artist.

Now you have fallen off the track.

Rusty said

If a power amplifier is
designed and marketed as a pure amplifier but adds audible
effects then it is poorly designed.

If you mean audibly uncolored when you say pure, ( I don't know of any
manufacturer that claims absolute purity) Then I would agree that the
manufacturer is misrepresenting the product. I think you are simplifying the
way amps are designed and evaluated though. Some designers actually hook their
products up to real world speakers and listen to the results and base their
success on what they hear.

Rusty said


However, I suppose it could be designed to deviate from ideal
amplification and marketed as "adding warmth to the treble" or
some other claim.

You are off the tracks again. You assume that your ideal is a universal ideal.
You are not even considering the fact that an amp is only one component in a
chain of colored components from musical source to final playback.

Rusty said

In that scenario it would be hard to call the
product poorly designed since deviation was intentional and
disclosed but it wouldn't be appropriate to call it just an
amplifier.

Depends on the situation.

Rusty said

I agree some audiophiles might enjoy the colorations
even though they deviate from the artists' intent.

You have no idea whether they do or don't. It would obviosly vary from
situation to situation.