In the rich text editor:
@tookiroshi
In a comment:
[tookiroshi](https://chowlings.com/user/tookiroshi)
For Names and Avatars:
In the rich text editor:
%tookiroshi
In a comment:
[](https://chowlings.com/user/tookiroshi) [tookiroshi](https://chowlings.com/user/tookiroshi)