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