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