In the rich text editor:
@creepyeevee
In a comment:
[creepyeevee](https://www.chowlings.com/user/creepyeevee)
For Names and Avatars:
In the rich text editor:
%creepyeevee
In a comment:
[](https://www.chowlings.com/user/creepyeevee) [creepyeevee](https://www.chowlings.com/user/creepyeevee)