I have another theory...
People who keep posting on the same account for a long time do so because they might actually have worthwhile things to say and are proud and vain enough to want to build a reputation. It's also possible that they just can't be arsed to create multiple accounts with the sole purpose of trolling an obscure, unknown forum, and have much better things to do with their time.
These people may or may not have ASPD, since intelligent behavior may or may not show in an ASPD case.
People who chop and change accounts probably have nothing better to do with their days than spending hours upon hours creating alternate accounts to troll people they are secretly resentful of. Due to them being too weak and too stupid to confront others face to face they resort to this cheap tactic where they remain anonymous and thus do not compromise themselves. In this case they have the backbone of a sea slug and are pathetic (and clearly have no social life, lol). It might also be that they are just switching around accounts and trolling others for the sole reason of being pathologically bored creatures who, despite this, can't find a better activity to entertain themselves than changing some pixels in a screen. I'd bet that if they DO have a social life, it is a terrible one. What kind of conversation would such a person hold? "Hey man, last week I spent fifty five hours sitting in front of my computer making fun of fake sociopaths, I'm so awesome lol".
But joking aside, my whole point is that ASPD and these account changing antics are not correlated. It's more a matter of intelligence and weakness, and as far as I know there can be both smart and stupid, and both strong and weak ASPD people.