Server admins!
If you're creating custom emoji, remember to fill in the section marked "Shortcode" as this will be the emoji's alt text description for blind people. Their screen reader software will be able to read the shortcode aloud so that they can hear what the emoji is.
If the emoji's shortcode includes multiple words, split them up with underscores or CamelCase, so that screen readers will be able to read each word correctly.