In the rich text editor:
@Morpho
In a comment:
[Morpho](https://chowlings.com/user/Morpho)
For Names and Avatars:
In the rich text editor:
%Morpho
In a comment:
[![Morpho's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/Morpho) [Morpho](https://chowlings.com/user/Morpho)