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