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