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