You can use the Wikimedia "pipe trick" to keep from having to repeat the username:
Wikipedia1 has some templates that are set up for this. You could just use the User link template
To be more "Twitter-like", there's the ping template (aka "Reply to")
This template is particularly helpful in discussions that are not threaded, to indicate which user's comment is referenced.
More information at Wikipedia:Notifications
1 English Wikipedia. Other language versions likely have different templates (if they have any).