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