In the rich text editor:
@creepyeevee
In a comment:
[creepyeevee](https://chowlings.com/user/creepyeevee)
For Names and Avatars:
In the rich text editor:
%creepyeevee
In a comment:
[![creepyeevee's Avatar](https://chowlings.com/images/avatars/410.png?v=1644063289)](https://chowlings.com/user/creepyeevee) [creepyeevee](https://chowlings.com/user/creepyeevee)