Look, going to HBO's web site is a work around to enable people to watch HBO when the Xfinity's sites buggyness prevents them from watching directly. If you are an HBO user suffering an inability to watch any or all shows be glad you have that as an alternative because some people who're trying to watch BBC America shows (like Orphan Black) can't because of one error or another and don't have another option since the BBC America web site does not offer streaming of episodes so it's either Xfinity or nothing for those unlucky people.
According to the Comcast telephone support people "The streaming service is provided as a free service to customers who purchase TV service from us and there is no separate charge for it." So you won't see a separate charge on your bill for it, it can't be purchased by itself and you can't discontinue it. So you may have a hard time convicing any regulatory agency that you are in some way being deprived of service or that "you aren't getting what you pay for" because you can't show in any way that you are paying for it, even though your TV subscription is subsidizing the streaming service. But if you want to go that route, your best bet is to complain to your local franchise authority which should be listed on your monthly bill and can vary state to state, region to region.
If you're having technical problems with the streaming service and you haven't received an answer from any of the official Comcast people here in a reasonable amount of time then I suggest you send a private message to one of them and see if you can get their attention.
- Norm