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