If a Windows update slows down some Windows code that C2 calls, the root cause is categorically with Windows itself. We might be able to work around it, and I'm looking in to it today. What is annoying though is when users blame us specifically for the problem, when all the evidence points to it not being our fault. It sucks enough that we're a small team left scrambling to cover up for Microsoft's mistake, and then having people blame us specifically for the issue and refusing to accept the possibility that it could be anyone else's fault (as if we're totally incompetent and all problems are obviously our fault)... that's just salt in the wound.
Basically I think this would be reasonable: "Hey Scirra, it looks like a recent Windows update slows down C2. This kind of sucks, do you think there's anything you could do to help?"
But this is unreasonable: "A recent Windows update slows down C2. OMFG C2 is so crap and is broken. WTF is wrong with Scirra. Why haven't they fixed it already? Do they even know what they're doing? Unbelievably poor service OMG!" (Maybe nobody used those exact words, but it's definitely the impression I get)
While this position is somewhat understandable, I think it's maybe a little revisionist to assume that even a majority of people pointing out the issue place blame 100% on Scirra. This is of course aside from the fact that it's not really anyone else's problem that Scirra is a "small team" (wasn't C3 going to subscription supposed to help alleviate this issue?) or that the changes Microsoft made were a "mistake." It's their OS. Scirra (and every user) is a guest. Software is designed to run on their OS, not the other way around (also an issue that still exists with C3 and Chrome/NW.js, before we get into that sales pitch).
As for quality of service - dismissing issues that exist because they're not Scirra's "fault" doesn't change the fact that when the issues were initially brought up, the response from Scirra was...well, pretty dismissive itself, in terms of the impact the software issue has on its users.
Anyways. None of the rest of the noise surrounding it - as in, the emotional reaction of Construct's users or Scirra's - really matters. You've said it's being looked into. Great! Thumbs up all around.