True, but they can’t cache a portion of the page that happens to be shared across every page on the website. If I go to a dozen different pages on the site, any in-http-page styles will be loaded a dozen times, while a separate style sheet will only be loaded once.

True but blogs are not Facebook. People generally don't visit thousands of pages. 1 visit and bounce is very common for blogs.

Visiting 1 article then bouncing is the most common pattern for blogs by a long way.

Also the amount of time taken to download a CSS file is usually much less than the round trip time for requesting the file. Especially in the p90/p99 end of the latency distribution. Here in Australia, I can download a 10kb css file in less than 1ms. But simply requesting that CSS file from America will take 200ms.

For a blog, inlining the css is absolutely the way to go. Especially if the css is small (which it should be!).