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