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