In the rich text editor:
@imie
In a comment:
[imie](https://chowlings.com/user/imie)
For Names and Avatars:
In the rich text editor:
%imie
In a comment:
[![imie's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/imie) [imie](https://chowlings.com/user/imie)