Suppose you find a bug in the kernel and come up with a patch. You email the patch to some kernel mailing list and ask for feedback. Typically, you will receive no response whatsoever, because no-one is responsible for responding. You can try emailing random developers and eventually maybe one of them will have mercy on you.
In Firefox and I think Chromium, you can file a bug, attach your patch, request review from someone (the UI will help you choose a suitable person), and it's their job to respond.