> Some songs were harsh and sounded too airy.

Chances are you hear production mistakes/errors in these songs that you simply couldn't notice on the "worse" headphones. And if you produce music yourself, such "better" headphones might allow you to avoid making such mistakes/errors.

I have a friend who bought a pair of magneplanar speakers which he then sold because he could hear the pianists fingernails hitting the keys in one of the pieces. I think he decided there was such a thing as too much fidelity.

That has to be his imagination, or else maybe he's hearing some other artifact that he's mistaking for a collision between fingernail and plastic. There's no way in hell he is actually hearing what he thinks he's hearing.

Not necessarily. With good quality recording and speakers it's easy to hear things like a finger hitting a guitar string just before the string moves, lips touching a microphone, etc. I started noticing these things years ago when I first bought Blue Note recordings.

One common problem with "headphone producers" is that they often spend too much time "cleaning" audio tracks and worrying about audio leaks.

In older recordings those things were masked by other instruments, sometimes even by the room's reverb or analog noise floor, or sometimes engineers just wouldn't care about soloing tracks as much because they were on the clock and studios were expensive as heck.

Now we have everyone with super low-noise digital recording, great headphones and unlimited (home) studio time. So people spend hours obsessing about things that weren't an issue before.

What makes you so confident that is the case? I listen to lots of classical music and certainly hear musicians breathing, even on older recordings. I would imagine fingernails on a keyboard are of a similar decibel level.

Same thing with the "vinyl sound". It's a proven fact they are worse a reproducing recordings faithfully than a regular well-mastered audio CD, let alone some high resolution FLAC. Vinyl distorts the sound. But it distorts it in a way people like.