Honestly, that experience was years ago, and I don't really care enough to raise a fuss about it just today, since their first-party router is "not too terrible".

About Xfinity in particular though, assuming someone else uses them, I did learn just recently that at least Xfinity allegedly offers a special decoder box (or something) that is, I believe, free of charge, and lets you hook up your router directly rather than putting it through theirs as a DMZ, and it's supposed to get them to not cut the line. Some self-install kit or something. You can only get it by asking over phone call.