> First, on Android 6+ you can just disable the contacts permission and everything works (although you obviously won't see your contact names).
This is very good.
> However, we also spend a lot of time thinking about this class of problems, as well as metadata in general. Right now things are playing out alright for one specific class of attack: [federal subpoena]
Good, so Open Whisper Systems has no metadata. Do any third parties retain metadata about Signal messages?
There's also the issue of mobile numbers. I get that more-or-less anonymous numbers are doable. But arguably, most Signal users don't have anonymous numbers. However, maybe this is a non-issue, if the only data available are "the date and time a user registered with Signal and the last date of a user's connectivity to the Signal service". Is that it?