I always applaud efforts at new typefaces, but unfortunately I feel this is a badly designed typeface that is
worse for legibility, not better. Addressing their three main points in turn:
> 1. Increased height for a better reading experience
A high x-height is good for coding fonts, but this x-height is now too high. To my eye, this is now at the point where lowercase letters are getting harder to distinguish from uppercase letters at a glance, so instead of increasing legibility it's actually decreasing it now. There's a good reason most other coding fonts haven't gone this high.
> 2. The shape of ovals approaches that of rectangular symbols.
Again, this is a problem because it makes letterforms harder to distinguish. It's important that the right side of a "b" look very different from an "h"... but if you make the right side of the "b" very straight, they look more similar. The whole point of letterforms is to be easy to differentiate from each other, not to make them more similar.
> 3. JetBrains Mono’s typeface forms are simple and free from unnecessary details... The easier the forms, the faster the eye perceives them and the less effort the brain needs to process them.
Again, this is just factually false, or else all books would be printed in sans-serif body text instead of serif. The main reason serif fonts are used is that all their extra "details" make reading easier, not harder -- because the eye has more clues to differentiate letters. Now because of resolutions of screens, sans-serif is still sometimes a better choice on computer screens, but this makes distinctiveness of letterforms even more important, not less.
For example, they choose a single-story instead of double-story lowercase "g", which is just harder for the eye to distinguish from a "q". Getting rid of the stem on a "u" also makes it less distinguishable, and harder to read. And so on.
I'm genuinely confused as to how the philosophy for this typeface was developed, when it seems to go directly against basic established principles of legibility.