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