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