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