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