Adrien - please take note that since you already wrote about
"everybody could update their environment and editors" to support unicode,
things like what you want (emojis in identifiers) can be supported
at programming editor (and plug-ins and extensions for those) level -
without impairing anyone else from working on your codebase.
You can just work on an extension for your favorite editor that
would transform certain escaped sequences into proper emojis.
If these escapes are themselves valid identifiers, there is no
stopping you and whatever enthusiast comunity you can raise
from having fun with the looks of "pyemojicode", and that wold
still allow people outside that community to interoperate with your code,
and all of the tools that use the static source would still work.
So, all you need is an extension to replace, at display time things liks
EMO_fire_ -> 🔥
EMO_heart -> 🖤
And so on. With a browser extension, or a site that acts as a proxy
to code hosting like github/bitbucket, enthusiasts could even see these
characters in internet listings. (The escaping sequence could be less intrusive as well,
your call - and it also would help getting those symbols input into the code to start with)