I appreciate this observation, this is something I'd like to keep an eye on. The reason I changed it is because many newer users we spoke to didn't understand why some comment bubbles were blue and some not. I assumed this to be because turning something blue when unread isn't a commonly used design pattern elsewhere on the internet (unless it's a blue circle next to the unread thing). My hope with the new design is that it will be more easily understood as "new and unread" since it uses a pattern more widely known to mean that. That said, I agree with you that it's less eye-catching than before, and if you feel like you constantly miss new comments due to this change, I'd love to know

Thanks for letting us know! Choice of typeface is no doubt a subjective thing and some will prefer the old font. In terms of inconsistency–one of the most popular principles for typeface combinations is the one I've gone with here–pairing a sans serif header with a serif body. This combination can be found online on places like Medium and Substack, and was already the case inside of Forum posts before this change. Typefaces are often even created in pairs of serif and sans serif that are meant to be paired this way.

This is obviously not a hard rule and you may still prefer other combinations (it’s not uncommon to use all sans serif on web, or all serif if it’s a magazine), and I'm definitely open to trying different things to improve legibility and tweak the “personality” of the Forum through typefaces (but it's not something I expect to prioritize changing right now)

Correct! There is a detailed article here about how Inter was made. It's open-source and designed specifically for screens.