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