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