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