In the rich text editor:
@Le_1923
In a comment:
[Le_1923](https://chowlings.com/user/Le_1923)
For Names and Avatars:
In the rich text editor:
%Le_1923
In a comment:
[](https://chowlings.com/user/Le_1923) [Le_1923](https://chowlings.com/user/Le_1923)