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