Good question. There's a Feedback tab in the top right corner of your interface. It gives you a popup window through which you can dispatch a message, which will be greeted by a message that reads, "We read everything, even if we can’t respond to every message", and a confirmation message will be sent to the e-mail address you supplied. Plus there's the FAQ, which is linked neither from the WordPress.com main page nor from the dashboard.
Myself, I believe that the users could provide a good deal of that support themselves: this worked for pretty much every weblogging application since Blogger got started in the previous millennium. A user forum would be a great thing.
Anyway. Your previous posts do have links, so when did this problem first show up?