Non-spam emails being sent to Spam

I've decided to start a new thread rather than add on to an existing one, though others also report this problem.

For at least the last month or two, Comcast has been routing emails from several email lists (e.g., from " [Edited: "Personal Information"]") to Spam. This happens with a few other emails as well--it has even sent the check-in link for a medical appointment to Spam. Some, but not all, obvious spam does get filtered out. (The proportion of non-spam to actual spam runs about 10 to 1.) The very best part is when I select a dozen or so emails in Spam and mark them Not Spam, and before my eyes they leave the Spam folder to go to the Inbox, and then get popped right back into Spam. I have to mark them Not Spam a second time, and then they stay in the Inbox.

I reported this, and got a call from an Xfinity tech/security guy with some excellent information, based on his examination of all the email traffic to me from a "problematic" list. Apparently email sent out  from this list's server to the list recipients generates a separate list or group for each new email. That is, each email has a different IP address from the last. Comcast's spam defense provider uses those IP addresses as its filter. Some of the addresses have been reported as sources of spam. This is why I may receive some emails from a particular thread, while others get routed to Spam.

This is also the reason it doesn't always work to add an email address to your Comcast contacts. This solution  is the only one Comcast offers, and it just is not reliable. To Comcast's system everything is not coming from [Edited: "Personal Information"], but from all those separate IP addresses. It would be better (the tech guy told me) if all of a list's emails came from the same IP address. Then that address could be added to one's Comcast contacts and the emails would be allowed.

So the response is for me to contact the lists and others that email me and ask them to do something different. This is completely inadequate. Why should I do all the work because a service that Comcast chooses to hire cannot handle industry-standard practices? Remember, this only started in the last few months, which suggests a new, flawed approach on the part of the anti-spam service. In general, this also seems like a flaw in the reputation-based approach to detecting spam. Online reputations can be manipulated, faked, misunderstood, or misrepresented whether intentionally or not. Doesn't everybody know this by now?

So there seem to be 4 actual workable solutions:

1. Comcast could do something about this.
2. I could check my Spam folder on the Xfinity Website several times a day to see what's been filtered out and restore it. Not a good use of my time, especially considering what I pay Comcast every month.
3. I could stop the general spam filtering and instead do it with manually created filters. See above under "my time."
4. I could abandon Comcast altogether. Been thinking about that anyway, but I kept coming back to, "Yeah, but it's my email address." Suddenly that seems like way less of a concern.

Please chime in if you've got similar experiences, or better solutions.