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