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