Maybe he means anonymous.
What’s the etiquette, or house rules, and what’s the interaction or banter between punters like?
Hardly anonymous unless you wear a balaclava!!

I guess you just have to take a risk that if you see someone there you know, you're both in the same boat and a conspiracy of silence would result, but in a city of 10 million people, it's pretty unlikely.
Whenever I've been to these or other parties there's no actual rules about talking, but you soon get the idea if it's appropriate to banter or not. I normally have some light hearted banter with the girls and other guests, quite a few of the girls initiate it. I have even made friends with some guys I've met at parties and continued chatting online here or elsewhere afterwards to share info and experiences. It would be weird if it was completely silent, but some guys do prefer to keep schtum.