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