Time stamping doesn't eliminate the risk that whatever service they're using to host the actual data could go tits up

Ultimately because of market forces I believe this is what will happen with the majority of non-financial data tied to Bitcoin. L2 doesn't have the same assurances of durability that L1 has though, so I can understand the desire to inscript on the main chain.

But you can perhaps make it thirsty...

Relays are basically servers. When you create a note, you broadcast it to a relay, which then broadcasts it to anyone using that relay