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