If I personally sent you a link to this article, it's because you were an @reply dope. You mistakenly sent a message that ended up in my @reply box.
Usernames are special, just like you. There's only one @skinny and that's me. Twitter keeps everyone sorted by assigning us all unique usernames.
Usernames are sort of like phone numbers. No two people have the same one. If you called up the wrong phone number, you would apologize. You don't get to mix digits in people's phone numbers or you'll end up talking to someone's granny in Montana.
You don't get to shorten usernames, just like you don't get to shorten phone numbers. Both have to be entered precisely. If you RT your friend who has the misfortune of having some stupid long twitter username like @skinnydabiznessinskinnyjeans, you shouldn't shorten said username to @skinny. Not only does your witty friend not know you retweeted them, I do. And I don't care.
You also shouldn't use the @ symbol to denote you're "at" a place unless you use a space. I understand Skinny's Lounge is a lovely venue, but please say "There's a hot show @ Skinny's Lounge..." There is a twitter account for them at @skinnysNOHO. Skinny's Ballroom is @skinnysBallroom. Please use these. They'd love to hear from you.
Don't put @ in front of random words. I don't even know what you're thinking.