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