In November 2022, we disabled the  emoji on mastodon.world, to avoid confusion for all the new users that came from Twitter.
Now that people have had time to get used to how the Fediverse works, we re-enabled the emoji.

But for new users: please remember there’s no such thing as official/verified accounts indicated by checkmarks… The only verification you have on Mastodon is that of the links to websites in your Bio. All other checkmarks/badges you see in usernames are just for fun.

One further remark on using emoji in your display name: Please be aware that this can be disturbing for people using screen readers.
@mwadmin thank you for mentioning that! A couple of simple emojis is probably not much of a problem but some people have a whole string of them in their names and my phone prattles on and on, reading the full description of each emoji. For example, "hand with light skin tone making the sign of the horns". Now string a few of those together…