It also depends on what level the creator is at.
Everyone is always improving, no matter the experience. But where you get that advice from becomes more closed off as you gain experience. If you're a newer creator, it probably helps to see advice from multiple places (such as the forums). For them, getting feedback in the comments (actually good feedback, mind I add) could be beneficial.
But a veteran most likely doesn't need that. They already know how to improve. They have mastered the art of improving. Even more, at this point, veterans already have peers they can refer to.
But it's not an echoing chamber -- veterans like these have hand-picked these peers. Peers that are at their level or maybe even higher. Peers of different skills and know what they're talking about. Peers they can trust to not only see where they're going with their stories but also tailor their critiques to help them get there.
Veterans can't stop people from providing feedback in the comments. But they're less likely to listen to them (as opposed to newer creators). I think the only exception I've seen is when it's the same feedback from several readers -- like a glaring error new and older readers are spotting in the stories. Other than that, they're more likely to ignore the comments and seek advice from peers on their level.
And I find that's usually for how they're presenting themes and tying plot points together. Course, you can argue readers help with this too, and I actually agree. But when you have a larger audience, everyone has their idea on how to present themes and tie plot points together. Feedback gets muddled, and it's a bit harder to pick good feedback throughout all of those comments. So veterans stick to smaller groups for better chances.
There's also the aspect of unsolicited advice as well. But from my perspective, if you've gained experience, the people you seek for help becomes more closed off.