If the Pennsylvania process is anything like Maryland's, they need to have a reply method that is pretty much available to anyone and use that. In the old days, it was easy because everyone used postal mail.
Once they have all the comments, a group of people has to go through each one, categorize it, determine whether it is something that can be done, whether it should be done and then either update the draft accordingly or document why the change will not be made.
While many suggestions will not be included and a reason will be cited, there are plenty of times when someone comes up with a good idea no one in the planning process thought of, resulting in changes.
Bottom line with the submission process, at least in Maryland, everyone needs to receive the same notice and everyone needs to submit through the same channel (email, postal mail) in the interest of fairness.
Also, there's the problem that some forums allow submission of massive amounts of comments from a single person in a way that makes it seem like there's a groundswell of support for something when it's really just a computer savvy troll looking to tip the scales in his or her favor.