Some of the highlights for me, as I didn't know these details before:
To make it even easier to get to just the right spot in your favorite app, we’ve built support for deep linking into iOS. A user can tap a link and it will open in the corresponding app if the app has been installed and supports deep linking. We do not associate this with your Apple ID, and Apple does not know which links you tap.
Apple does not know what devices you’re controlling, or how and when you’re using them. Siri only associates your HomeKit devices with your anonymous Siri identifier, not you personally. Apps supported by HomeKit are restricted by our developer guidelines to using data solely for home configuration or automation services. Data related to your home is stored encrypted in the keychain of your device. It’s also encrypted in transit between your Apple device and those you’re controlling. And when you control your accessories from a remote location, that data is also encrypted when it’s sent. So HomeKit doesn’t know which devices you’re controlling or how you’re using them.
On Siri's suggestions:
Certain features do require real-time input from Apple servers. For example, event addresses and a user’s location are sent to Apple so that we can provide accurate Time to Leave predictions that take into consideration traffic and local transit schedules. Information like a user’s location may be sent to Apple to provide localized suggestions as well as relevant news and search results. When we do send information to a server, we protect your privacy by using anonymized rotating identifiers so that searches and locations can’t be traced to you personally. And you can disable Location Services, our new proactive features, or the proactive features’ use of your location at any time.
One thing's for sure – Apple is going all-in on protecting privacy and user data as much as possible.