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