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