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