What he is trying to say is that you will be much more satisfied with the Eterna if you don't go about nit picking about earphones as certain people tend to.
The Eterna's are spoken of as having a much more 'musical' sound. In pseudo-audiophile terminology this means that they have a colored sound. They emphasize and de-emphasize certain frequencies.
So called audiophiles do not like this fiddling around with frequencies and prefer devices that can playback their music exactly the way it was, hence the term Neutral iems.