In the rich text editor:
@Stiv
In a comment:
[Stiv](https://chowlings.com/user/Stiv)
For Names and Avatars:
In the rich text editor:
%Stiv
In a comment:
[![Stiv's Avatar](https://chowlings.com/images/avatars/455.jpg?v=1644063294)](https://chowlings.com/user/Stiv) [Stiv](https://chowlings.com/user/Stiv)