This has been discussed before. While that sounds non-problematic, it will in fact make it nearly impossible to have any useful photographic coverage of a Debconf. No signals on badges or lanyards are visible enough to be able to notice a person who do not want to be photographed in the public of a talk, in a hacklab, in C&W party or in corridor discussions. Either this will be a false promise to attendees or there will be no photos of that Debconf. What we have in the current code of conduct is already the agreed compromise.
In general, if anyone does not want to be photographed, it should be sufficient for that person to ask the photographers. We have handled this before, even in the cases of photographers not really wanting to cooperate initially. And asking to take down or modify a photo containing themselves must be honored, of course. In addition it is expected that photographers do not take photos of children, unless their parents explicitly ask for such photo to be taken.
This is a compromise between attendees rights not to be photographed and the needs of the community to capture and preserve memories and documentation of the events. These photos are often used for many decades to show the great spirit of Debian community and the value of Debconf as an event in bringing that community together (including to potential sponsors).
In past Debconfs there were some additional, workable, measures taken to allow for more privacy - both from photo and video recording, by designated a hacklab, a talk room or even a particular section of the main talk room as "no video zone" and ensuring that it will not be filmed by the video team cameras in addition then it was also promised that no photos will be taken in these few rooms. Unofficially this practise continues on in the quiet hacklab.
Statistically I can say that usually at past Debconfs 2-3 people have asked me not to take their pictures and around a handful of photos across like a decade of Debconfs had to be removed or modified on request of people in the photo. And both of these numbers have been decreasing over time.