I had thought to chat with a specific user, but I don't see any way to invite anyone to chat, and I am wondering if using the @username formulation will cause a notification to appear in a user's notification queue?
If you create a chat room you can invite a user to it. The limitation is that the user has to have used chat before, in order that they have a chat user to invite.
First of all you have to find the user you want to invite.
- visit the chat.se users tab
- type in the name of the user you want to invite:
- select that user by clicking on their name
Then an invitation is sent by the system to that user, which appears in their SE inbox, like comment pings do.