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