Um, I'm a fraid to ask, but what exactly does "getting HD'd entail? Does it go beyond the defamation of an anonymous avatar, and affect your RL reputation or that of other avatars?
Sometimes, if they're lucky, it does. And to both.
I would have to say, the only other way I can find to get out of it, if it has a chance of going that far, is to stand up to the attack, and find a way to convince them that it was a Xanatos Gambit (or Roulette if you want it to appear accidental and unexpected; though wanted nonetheless) you pulled on them out of boredom; and that you're much smarter than all of the attackers, and call out all of their attacks (while supposedly joking along, and being in on some of the jokes and taking on the hits with pride), force an interview if you must as well (psyching them out whether they believe you or not about your personality) humiliating them in the process (by already rendering all attacks worthless since you admit to mostly flaws, and minimize the amount of jokes they launch at you. Forcing them to recycle old jokes to just plain sad/lame levels. Even to the point that even the victim is getting bored of the same attack. Essentially, it's like a fighting game, and making your opponent button mash one button like mad as the only way to win. A cheap and boring method.), and appearing as if the attack had no effect on you, and you were acting pathetic just to see how many trolls you can wrangle.
If you can convince them to doubt that you were pathetic the entire time, and are indeed a seriously complicated and fucked up person/troll; then you have won. All you have to do is admit the fact: you are a much better troll than them, and you were the 'victim' (which in truth, you actually were). If the thread dies within the next half hour, then the success is more certain. If it gets locked by the next day, it worked. Kudos is given if other members (especially those involved in the attack) are convinced that the whole attack is no longer funny, and begin to fight amongst themselves while you walk away from the furball with barely a scratch on you. You can also be the bigger person and just walk out as they continue to brutalize, showing you are indeed the bigger person, and don't give a fuck what they think. They change your avatar and such later; you can just continue acting nonchalantly, and bother them with it. Nothing bugs a bully more than their victim being bored with their "pitiful" attempts to get their attention.
In a sense, what was once a pathetic person, so to speak, is actually one very dangerous person to come across. A troll that outclasses an entire forum made of trolls; out of boredom (As the illusion should show: this is an activity done with their free time. They do this regularly. They're A-class at least.). A cookie jar to those who pull it off as a successful bluff. A can of worms instead if it fails.
It sort of reminds me of a quote from "The Chronicles of Riddick":
"In normal times, evil would be fought by good. But in times like these, well, it should be fought by another kind of evil."
NOTE:
If you have any family or important people you don't want to take notice of the attack, I suggest you act fast. But sometimes, letting them attack for a good while first is also a good move. It would look as though you've been reading their actions, letting them build a sort of confidence; not expecting any response. And then *WHAM*, victim responds with a confident demeanor, and clearstheir name the only other way they know how. By out-performing his attackers. The classic backlash.
Oh yeah, and to further convince them that it was all a trap, take your time leaving and eliminating all related accounts and IDs (for example: wait a month, and eliminate all related accounts within the same day after the time has passed. Remember to not respond at all for a short while. You know, in case of any PMs regarding apologies, or BS callouts.). Make them think that it was all indeed a really complex trap setup. Just an added bit of spice to make them more paranoid. It's like those movie scenes where the villain or anti-hero walks away from a car or building in slo-mo, and the building/car explodes moments later, and the person doesn't even flinch. Have that kind of cool, and remain incognito, and watch the paranoia, and the confidence of the attackers unravel. Oh, and it's best advised you change IP address ASAP too to further guarantee the skillful backlash.