+1; Reasonable. But I don't know what font is better for emojis. Is your list of CSS also good for Sphinx?

Hmm... it seems there are no default font settings in basic theme. So adding fallback fonts affects to default font...

We could prepend the list of emoji fonts with a list of system fallbacks from here https://devhints.io/css-system-font-stack.
Also, there's a font-family value system-ui which is supported in modern browsers: https://caniuse.com/#feat=font-family-system-ui.

The trick is to have emoji fallbacks last in the list and having system fallbacks before should be fine.

Is your list of CSS also good for Sphinx?

I suppose so. I've tested it on Alabaster (sanitizers/octomachinery@787226b / https://docs.octomachinery.dev/) and also I used DevTools on packaging.python.org to inject these fonts at the end of the existing list.
It all worked well. I also use this fallback in Reveal.js slides.

N.B. Some emoji fonts (if they contain only emojis) are okay to bring to the front row but there's others that have emoji-like numbers that appear in place of legitimate digits that are expected to appear in the same style as the surrounding text. For texting, I just edited CSS rules via DevTools by removing fonts from the list one by one to see what happens...

Some refs:

• https://www.client9.com/css-color-emoji-stack/
• https://css-tricks.com/it-all-started-with-emoji-color-typography-on-the-web/