Hello.

I suggest to add "Reply" button (near "Like" button to each comment) that will automaticaly add tagging "@username" to comments form.

Or may be instead of "Reply" can be used RealName (click on RealNmae to TAG; but click on avatar to visit profile page).

It will let to tag users more faster and easy.

Most users don't know how to work with "@".

I also noticed that at VK.COM this feature works not only when user click on "Reply", but also when user press on comment text (red area at the screenshot).

Thanks.