In this case we've banned the account because you can't have a trollish username. Those end up trolling every thread the account posts to.
In other cases it's probably because your new accounts are breaking the site guidelines. If you're sincere about wanting to use HN as intended, you're welcome to email hn@ycombinator.com and we'll look into it for you and be happy to help. But could you please not create accounts to break the site guidelines with?
