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