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