In the rich text editor:
@FroggiFriend
In a comment:
[FroggiFriend](https://chowlings.com/user/FroggiFriend)
For Names and Avatars:
In the rich text editor:
%FroggiFriend
In a comment:
[![FroggiFriend's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/FroggiFriend) [FroggiFriend](https://chowlings.com/user/FroggiFriend)