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