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