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