In the rich text editor:
@Mio
In a comment:
[Mio](https://chowlings.com/user/Mio)
For Names and Avatars:
In the rich text editor:
%Mio
In a comment:
[![Mio's Avatar](https://chowlings.com/images/avatars/259.png?v=1644063270)](https://chowlings.com/user/Mio) [Mio](https://chowlings.com/user/Mio)