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