In the rich text editor:
@grimgnostic
In a comment:
[grimgnostic](https://chowlings.com/user/grimgnostic)
For Names and Avatars:
In the rich text editor:
%grimgnostic
In a comment:
[![grimgnostic's Avatar](https://chowlings.com/images/avatars/343.jpg?v=1644063280)](https://chowlings.com/user/grimgnostic) [grimgnostic](https://chowlings.com/user/grimgnostic)