Nice, but can I see the source code, if so, where can it be found?

EDIT: works again after the update.

The code of the extension is minimal and straightforward, but if you don't want to install it, alternatively you can add this rule to your uBlock Origin filters to replicate it:
||discord.com/api/*/typing

thanks, it's nice. i don't like it when people see me type, so this is great, especially since i'm not constantly using the client version of discord where you can use plugins to disable things like this.