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