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