alt Hacker NewsNot exactly automatically.
Seeding is opt-out, not opt-in… but it is usually a default that has to actively manually overridden. Most users never touch those settings. The average pirate downloading a torrent is seeding whether they know it or not.
The protocol absolutely does not enforce seeding. A client can lie to the tracker, cap upload to 0k. BitTorrent has no mechanism to compel one to share. Leeching a file, downloading and sharing no forward packets is possible. While the "social contract" of seeding is entirely a norm enforced by private trackers and community shame. It is not the protocol itself.
seeding is not the only way you actually upload
you're uploading before seeding, and i'm willing to bet Meta weren't seeding but, as they correctly stated in that regard, they're sharing even when they try their best not to because of the way the protocol works as zero-upload is typically impractical for any significant size files
some trackers will additionally penalise you for not sharing file parts, but this depends on the tracker