In case this is real.
When making a post you can leave the Name, Email, and Subject fields empty. Password too but that can come in handy if you want to delete your own post.
>How do I delete my account?
As far as I know you can't delete your account. Just forget about the password and you are done basically.
Note: to use endchan as simple poster, users don't need an account, only if they want to create and manage a board.
Note 2: when posting the Password in the posting form shouldn't be the password for the account if one made an account, but should be safe enough so others can't just guess it. I find the best practice just not to add a password and think a moment what you post first. And suck up mistakes.