Here's a better pitch based on your feedback and maybe more tailored to the Hacker News crowd.
The Internet is broken as content primary pools behind walled gardens like Facebook and Twitter. These platforms are not open in the sense that the metadata is locked up inside them. Additionally, they're not very respective of the rights and privacy of their user base.
Polar tries to reboot this by building out a generic datastore model where users can share content with anyone of their backend datastores.
The information/metadata model is free and portable and content and metadata can flow across networks.
Polar is implemented as a 'read it later' style app similar to an RSS reader where you can add documents directly (vs RSS subscribing to a feed) and manage them and keep track of your reading.
The key part is that Polar adds a metadata layer on top of PDF and the web and you can exchange the metadata with other users (still being implemented, initial sharing should ship next week).
This means that you can add content from anywhere on the web and also share it with anyone else.
We also archive the content and the actual content archives can be exchanged too. This means if anything is ever deleted you still have a copy.
Polar also adds support for features like spaced repetition (never forget anything) and incremental reading (never forget what you're reading and where you left off) to encourage you to use Polar to manage all your reading material.
The idea is that if people have a very valuable app to keep track of their content that they're more naturally likely to use it which means that the sharing and open content vision is directly powered by users.
Right now we support local mode and cloud powered by Google's Firebase. We're planning on adding other backend providers like Filecoin but we have to take baby steps now because we're still an early project.
Polar's design (though not yet implemented) can support end to end encryption and key sharing for group encryption. This means we can support fully end to end encrypted datastores.
You can use a system to store your data (that you don't trust) and only you have the key.
Additionally, if you want private group sharing we support one to many encryption where you can fan out content to anyone in a fully private group.
It's important that this remains Open Source so that we can rely that Polar isn't just going to vanish.