They didn't ignore them. They addressed them, rejecting out of hand a ton of issues that were sometimes pretty crazy anyway. There were some really oddball submissions along with others that were very good ideas. They did adopt several ideas that came from comments, including my own and one from Reed Lee. Before the last round of comments there was no obligation to record the actual date of photography, which made the whole thing ineffectual to determine if child porn was created. The whole idea for third party custodians was first proposed by Reed. You can read how they dealt with all of those comments in a 100+ page set of comments linked here as the December 18, 2008 Promulgation.
http://www.xxxlaw.com/section-2257/index.html
You can see how they addressed comments back in 2006 in a huge table correlating their responses to comments to the actual regs on the same page lower down, Five Column Table.
They can't ignore them. But they have discretion to do what they reasonably want.
However, in this case, they've set themselves up for disaster. Their basic methodology is so flawed that a court would laugh at it. This is the time to bolster the case of the huge economic and manpower burden.
No, it would NOT be pointless to respond. It will create an administrative record that lawyers can use to challenge this in a frontal assault or in defense of individuals charged.
The guy in charge of all of this, whose email address is in the published notice, is no idiot, miles away from that.
And who knows, it just may so shame them to have the truth published that it may cause changes here and there to avoid the embarrassment of having to defend obvious nonsense while standing in front of a federal judge.
All your comments must be published by law, even the anonymous ones, so they can't deep-six the Comments submitted by industry and public.