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