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