There seem to be several things not yet discussed on this thread that seem IMO to be important.
The first is that the ear interprets harmonic distortion as tonality. For example, the 2nd harmonic of some tube amps is why they sound 'warm' or 'lush'. Another example is the trace amount of odd ordered harmonics typical of a solid state amp with lots (+20db) of feedback; they will sound 'hard' or 'bright'.
(BTW, the lower orders, 2nd, 3rd and 4th, are proven to not be irritating to the human ear. But not irritating simply means they are musical; IOW that is not to say that they are inaudible!)
The second is that negative feedback is used to control the speaker in two ways: by altering the power output of the amp depending on the speaker impedance at that frequency, and by providing increased damping.
So here are the problems with adding feedback to any amplifier. I did note BTW that this seems to be ignored in the article in the OP. In fact I've seen a lot of engineers hide behind theorems (Shannon, Nyquist, et. al.) to explain why this is not a problem, and that problem is the delay time between input and output of the amps.
The reason the theorems don't work is they don't apply. They apply in a theoretical world where propagation delay in the amplifier circuit does not exist. But almost any oscilloscope can measure this delay time in almost any amplifier made. If we could build amps that had no delay (propagation) delay, then feedback would not cause the problems it does.
However we have to live in the real world, and experience has shown that being pragmatic about that fact reaps big rewards.
In this case all amps have propagation delay so the application of loop negative feedback will have the benefits that Kijanki has described, except for a tiny bit of odd-ordered harmonic that is considered 'negligible' by degreed engineers. This 'tiny bit' of distortion can be modelled as a 'ringing' effect in the amplifier. Chaos Theory has something to say about this, I will go into it if people are interested.
It is the mark of a good engineer to know when to use the word 'negligible' correctly! In the case of 'negligible odd ordered harmonics added' the word is misapplied. The reason is the human ear is more sensitive to the presence of odd ordered harmonics than it is to almost anything else. This is because the ear uses odd ordered harmonics (present in any sound) to figure out how loud that sound is. If the odd orders are slightly louder due to electronics, the resulting sound will not only sound louder than it really is, it will also sound brighter. Its funny that an engineer might know how to design the feedback loop but be completely uninformed about how the ear will perceive the result!
Really the only way to get around this is to get rid of the distortion. But as Nelson Pass points out in a distortion article on his site
https://passlabs.com/articles/audio-distortion-and-feedback you can add more feedback to reduce that distortion but you need to add more gain (adding to the distortion) to do it. You are chasing a carrot on a stick.
With regards to damping factor: Some speakers require high damping factor (up to 40:1) and some speakers want very little (0.1:1 and yes you read that right). No speaker made needs in excess of 40:1. The chief engineer of Electro Voice wrote a two-part article on this some decades ago and the facts of that article have not changed which is how it usually works with facts. I will try to dig up the article (its online) if anyone is interested.
For me there has always been a bottom line, which is that if your speaker requires that the amp have feedback you won't be able to get it to sound like real music because the amp is violating one of the most fundamental rules of human hearing.
How do you get around this if you don't want the system to have colorations (audiophiles talk about these colorations all the time; warm, rich, soft highs, wooly bass, etc)?? The fact of the matter is you have to do everything in the book that you can to reduce distortion without using feedback, and stick to speakers that don't expect a low output impedance from the amp (BTW the crossover design rules can be quite different!). A fully symmetrical design will, for example, cancel the even ordered harmonics (otherwise the 2nd will be predominant in any design, tube or transistor). The even orders will thus cancel not only in the output of the amp but in every proceeding stage. That leaves the odd orders, and if you are careful they will not be generated.
There are plenty of other techniques BTW. In addition any ZNFB amp, IMO should have a very low IM distortion figure if its done right, because IM is very audible. That is very possible in a ZNFB design- we get numbers that are as low as many amps with feedback. IM distortion (or lack thereof) is a function of linearity.
