So can you cancel without being hassled excessively or not? The founder of the business just stated right up the thread there that there's no self-service cancellation and they always exchange a few e-mails with someone who is cancelling.

Personally, I am usually happy to give feedback to fellow business folks, and I wouldn't be offended if someone politely asked for it from a service I was cancelling. However, if a single reasonable action to cancel and no further contact resulted in my card being charged because I didn't play along, that service should not expect a happy outcome.