The grand-parent comment was arguing that this distress can be objectively catalogued by someone other than the patient, and that the patient may themselves be unaware.

This does seem to be true for some forms of mental illness, depending on exactly how you define distress. For example, someone going through an episode of mania (such as in bipolard disorder) is typically subjectively extremely happy with their state.

Mania.

But mania without the downs is basically what we are all going for.

Psychopathy

But psychological manipulation without the downsides is basically what we are all going for.