Subtlety would be key. Let's think about this. You're a pathetic loner who masturbates to and craves attention. But every time you create a troll account, you rile up the board and get banned. While that's a thrill it's short lived. You need a steady stream of moderate attention. Something that get's you what you need but also doesn't get you banned. So why not create an account that only sometimes or partially pisses people off through a more complex character.
You can spot a troll because it's essentially a stock character. For those of you that don't know, a stock character is one-dimensional. Like the burly trucker, or the grimey pothead. They're one note, little to no room for character development. The reason being most of these attention-masturbators can't create a character that complex. Ichoosenobreaks was an obvious troll for that reason. But these guys are easy to spot and you keep getting banned.
The main character is the person that can go through emotional development. They can be sad, happy, learn something, etc. You still stick to your character in some ways. Homer Simpson lives and learns, but in the end he's still an alcoholic.
And that's the key - you're subtle. Sometimes you actually make a trivial contribution or two. But you still spice in annoyance, or whatever get's you your attention. Maybe you piss people off with your agressive opinions you can't back, your ignorance to obvious shit, innane questions that could easily be solved through google,repeated bumping of pointless threads, whatever your angle is.
You could do this for months, years if you wanted to. You could even give yourself a backstory that has a lot of people overlooking you. You could be very young, sick, mentally handicapped, extremely foreign, what have you. Then you'd even have people sticking up for you. "It's not their fault their a terrible poster, she's extremely foriegn!" It would be quite easy to hover below the line of bannable, while still forcing attention upon yourself.