If I buy a domain, can I write anything to a TXT record? Can I publish videos there? I base64-encode them, then I split them in chunks and upload to giant set of TXT records.
You're both right from where I'm looking.
I've been saying that DNS is the perfect mechanism to assert NIP-05 identifiers (and Lud-16 lnurls, and even BTC addresses) for quite some time.
In the case of NIP-05/LUD-16 The .well-known/URI scheme is limiting - and I would also argue, less secure than, say, a DNSSEC signed zone.
While true that DNS is "centralized" ultimately at the root level, there is no content or participant level censorship there - the DNS tree is somewhat like a federated namespace AND there will in time be more decentralized namespaces outside of the IANA tree within which one could pin their NIP-05 or LUD-16 ids.
None of these arguments have convinced the people it needs to (*cough* nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 *cough*) - and to his counter-points, I do somewhat get it).
It is possible that somebody, someday could propose another NIP entirely for the assertion of NIP-05-like id's (they would look exactly the same) via DNS TXT recs.
It is not obvious or probable that such a NIP proposal would succeed.
At the risk of sounding repetitive, I'll refer to my previous article on this sort of thing here (and there are a few threads on Github somewhere):
https://bitcoinmagazine.com/technical/simplifying-bitcoin-addresses-dns
Discussion
Technically, you could - but that's not really what anybody is suggesting here.
They're suggesting that instead of telling people "come find me on Nostr at fe6877b5bb095e9d474fe7ffe9b211da985fdf0349ea61a55bb643545bf8bcfa"
You tell them "find me as markjr@bombthrower.com" and being able to do that without plunking a flat file down on https://bombthrower.com/.well-known/nostr.json but by simply publishing the hexval via DNS TXT