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