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