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