I'm glad to introduce a new functionality mod I have added to the site. Its called Mentions.
It allows you to "tag" other members in your posts. Simply type the @ symbol, followed by their username. As you type, a list of usernames will appear and narrow down your search, so you can be sure you're typing it correctly. Once you have posted they will be able to see it under the Mentions page on their profile (see image below).
The "tag" will also become a direct link to that persons profile. Neat huh?
You also have the ability to turn on email notifications for when you are mentioned.
Give it a shot!