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