In the rich text editor:
@Polly0Possum
In a comment:
[Polly0Possum](https://chowlings.com/user/Polly0Possum)
For Names and Avatars:
In the rich text editor:
%Polly0Possum
In a comment:
[![Polly0Possum's Avatar](https://chowlings.com/images/avatars/default.jpg)](https://chowlings.com/user/Polly0Possum) [Polly0Possum](https://chowlings.com/user/Polly0Possum)