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