I'm not a huge fan of mandatory emoji in commit messages either, but this is a poor excuse. A Git commit message can contain any sequence of bytes except for a NUL byte. It can even contain invalid UTF-8. Tooling that doesn't treat commit messages like this is dangerously fragile. God forbid anyone accidentally pastes “typographer’s quotes” or text with diacritics into a commit message and breaks the build.

On the plus side, I don't think this style guide will break your CI. It seems to be taking advantage of GitHub's text => emoji substitution, so other Git tools will just see the text form (eg. :sparkles:)

Ah, but is that a problem with the commit messages, or with the CI systems?

this guide doesn't use any fancy-unicodes... I'm guessing that :penguin: isn't a unicode-penguin character, but some emoji supported natively by github

(e.g. :+1: means thumbs-up, but that's native to github / shows as :+1: to non-emoji-supported cli/browser/etc.)