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