User mentions are a great way to include other WordPress.com users within your posts and comments, and ensure that they know about your mention. Mentions work similarly to how they work on Twitter, where you use an “@” symbol, and then someone’s username.
How It Works
When you’re writing a post or comment, if you enter a space and then a “@” character, you’ll be presented with a list of possible people to mention. We’ll try to suggest people who you might like to mention, based on those relevant to the blog on which you’re typing.
Currently, you can only mention other users of the blog you’re posting/commenting on.
If you pick someone from the list, or finish typing their username, then when you publish that post/comment, the name you mentioned will be linked to a page that lists all posts on that blog mentioning them, and that person will receive a notification. Their mentions page will look similar to an Author Archive page (the exact layout depends on the theme you’re using). The mention itself will look something like this: @wordpressdotcom (but with a link).
When you are mentioned in a post or comment by someone else, you’ll get an email that tells you about it, and links back to the place where you were mentioned. You’ll also get a toolbar notification in your WordPress.com admin bar. If you’d prefer not to get an email when you’re mentioned, then you can disable that notification via your Notification Settings. You can also subscribe to IM notifications via Jabber.