[bluedel]

the lack of capitalization (and occasional omission of punctuation) was already a big thing on tumblr / twitter 10 years ago, especially in some anime and LGBT-adjacent spaces. I don't think jyn got it from Sam Altman, and I don't think he had that big a role in popularizing it.

[int_19h]

It was a thing 25 years ago already in SMS and IM.

[monerozcash]

Before smartphones, it seems to have been the standard for just about every form of instant messaging. Well, morse has no capitalization and telex would typically have been uppercase-only too, but I think we can still count those?

I suspect that this is just something that happens naturally, for shorter-format messaging typing in sentence case probably offers no added readability and tends to get dropped over time.