> Since this is a frequent occurrence, wouldn’t it be neat if we could do this kind of “archive interesting article” thing using IPFS? Maybe even do it automatically when submitting it to HN such that it could tell HN itself to grab a copy?

Saving things to the Wayback Machine at the Internet Archive is a far superior solution than IPFS. IIRC, IPFS only keeps things as long as they're popular, which has famously resulted in things like most NFTs pointing to dead links.