In the rich text editor:
@Harta1
In a comment:
[Harta1](https://chowlings.com/user/Harta1)
For Names and Avatars:
In the rich text editor:
%Harta1
In a comment:
[![Harta1's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/Harta1) [Harta1](https://chowlings.com/user/Harta1)