In this new feature, mentioning would work the same, but with the added feature of being able to put the username into less-than and greater-than symbols, like "@<banjo2>", but it would still display as @banjo2 once the comment/shout/whatever is sent.
This may sound pointless, but here's the purpose:
• Allows you to mention users with spaces in their names, such as @<Star Shadow> or @<Gemini Guardian>
• Allows easier mentioning in parentheses or other punctuation (I'm fairly sure it wouldn't work if I did @banjo2)
This is actually at odds with my own solution to this, ?id=12070.
Also, Hull said something to the effect of "I don't wanna fix this since spaces were never supposed to be in usernames in the first place. I don't wanna bend over backwards just for their sakes."