You can work around that via a Live Template. Go to Settings -> Live Template, click the "Add"-Button (green plus on the right).
In the "Abbreviation" field, enter the string that should activate the template (e.g. @a), and in the "Template Text" area enter the string to complete (e.g. @author - My Name). Set the "Applicable context" to Java (Comments only maybe) and set a key to complete (on the right).
I tested it and it works fine, however IntelliJ seems to prefer the inbuild templates, so "@a + Tab" only completes "author". Setting the completion key to Space worked however.
To change the user name that is automatically inserted via the File Templates (when creating a class for example), can be changed by adding
-Duser.name=Your name
to the idea.exe.vmoptions or idea64.exe.vmoptions (depending on your version) in the IntelliJ/bin directory.
Restart IntelliJ