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