They are regional indicators, groups (usually pairs) form the flags, which are in fact multiple characters but behave like a single glyph in a text editor. You can input them and other Unicode “fonts” using the Irregular Expressions keyboard. Their rendering differs wildly but they are usually small caps, sometimes in boxes (dotted or blue) or bold/filled blue themselves.

For people using Lemmy clients that only show usernames, @Kolanaki@pawb.social’s display name is “🇰 🌀 🇱 🇦 🇳 🇦 🇰 🇮”. Without spaces nor zero-width non-joiners, the name becomes “🇰🌀🇱🇦🇳🇦🇰🇮” (LAos, NAmibia, KIribati) - you can copy the name into an editor, delete the spaces yourself and see the flags appear. I’d be really surprised if any automatically inserted ZWNJs.

They’re in the unicode table thing. "Character Map"utility in Windows should have them. There’s also online things to just turn regular text into fancy text.

The O, however, is the hurricane/swirl emoji. 🌀