In the rich text editor:
@Nox
In a comment:
[Nox](https://painted-relics.com/user/Nox)
For Names and Avatars:
In the rich text editor:
%Nox
In a comment:
[](https://painted-relics.com/user/Nox) [Nox](https://painted-relics.com/user/Nox)