In the rich text editor:
@Luckyy
In a comment:
[Luckyy](https://chowlings.com/user/Luckyy)
For Names and Avatars:
In the rich text editor:
%Luckyy
In a comment:
[](https://chowlings.com/user/Luckyy) [Luckyy](https://chowlings.com/user/Luckyy)