If you want to use the @ mention functionality for linking a user name to a user profile, which includes the nice pop up modal when you hover over a user name, and (I assume) triggers the system email for when users are mentioned in a topic…

Here’s how you can do that via HTML:

<user-mention data-id="user id number goes here"> text you want linked (probably their user name) goes here </user-mention>

My use case for this is automating replies with Zapier (there’s a “Create Reply” action that you can format with HTML). I want to @mention users in the automated reply, similar to how I might if I drafted the reply myself. 

There are potentially other use cases where you might