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