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