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