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