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