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