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