In the rich text editor:
@Fosbat
In a comment:
[Fosbat](https://chowlings.com/user/Fosbat)
For Names and Avatars:
In the rich text editor:
%Fosbat
In a comment:
[](https://chowlings.com/user/Fosbat) [Fosbat](https://chowlings.com/user/Fosbat)