I'm not involved with HN, but it seems likely that many smaller venues esp ones that aren't big money makers, including most mailing lists and small sites like HN would be advised to discontinue operating if exposed to this kind of extraordinary liability over content which they had no knowledge of.

"Actual knowledge" should be your preferred approach to your concern... but nothing will probably solve your problem because extremely well funded platforms are substantially immune to the law in any case, just as they're immune to common decency.