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