This is a thread that could go back and forth for a long time with personal opinion and regardless of which side of the fence I sit on, the simple facts are that there is not now nor will there be a written policy that people have to agree to, to NOT take their heads off. This would be applying a very strict dress code which could both be very difficult to actually police, and also would be an incredible breach of personal choice of attendees.
As per earlier replies, how people wish to represent themselves in their fursuits is entirely down to them. Ultimately, it is their character, their property, and their right to choose. I cannot even agree that this is a cultural difference as has been suggested as I often see headless suiters at EF, MFF, and FC, I think its more so a case of what impact it has on the inidividual and what we choose to see/not see and/or not comment on.
The one point I would make ultimately is that this year, as with last, it was very humid and muggy due to the rain followed by a heat wave. This is certainly reason enough for anyone to take their heads off, and whilst it might 'ruin the magic', again irrespective of my own views on this break of character, the attendees health and well being, and right to socialise and have a good time, is the conventions primary concern.