Interesting article.

(Speaking generally, not just BOLT12/onion messages): Ultimately, in a network you have to choose between fixed identities and cost to prevent Sybil attacks. But the cost can be somehow deferred rather than an actual direct satoshis payment to the service provider.

It'll be fascinating to see how it plays out; people don't even seem to agree much about probing (I seem to recall Christian Decker arguing in favour of it, and clearly it has a lot of usefulness, but costless probing is just not going to be robust long term).