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