looks fine to me on linux, surprisingly. though i doubt that the designers tested on a linux box with a tweaked fontconfig

edit: here's a comparison with helvetica https://i.imgur.com/BJlHQhf.gif

CSS is seeing this stack on FF for me: "TwitterChirp", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif

I'm getting Roboto on Linux which (a) looks great and (b) is very similar to the new font

Are you actually getting Chirp? Seems some Linux users are not. I'm on Chrome on Ubuntu 20 and I do get Chirp, and it looks quite bad IMO.

yup TwitterChirp is the computed font according to firefox

Has to be a BeBox.

I'm on a Mac, and I'm not getting any issues. Perhaps its machine or OS version dependent? Or browser dependent?

Looking good on iOS.

Looks good on my S10.