In the rich text editor:
@Mayo
In a comment:
[Mayo](https://chowlings.com/user/Mayo)
For Names and Avatars:
In the rich text editor:
%Mayo
In a comment:
[![Mayo's Avatar](https://chowlings.com/images/avatars/1248.png?v=1655939249)](https://chowlings.com/user/Mayo) [Mayo](https://chowlings.com/user/Mayo)