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