This is the most pertinent part.


Lightning transactions are as the text decribes, in essence zero-confirmation Bitcoin transactions that are not broadcast publicly like on-chain transactions are.


But this does not make them as insecure as zero-conf on-chain transactions, as they use a combination of time-locked funds and mutually exchanged revocation secrets to reinstate the security that zero-conf on-chain transactions lack.

So, it's fair to say that Lightning is less secure than on-chain, but more secure than zero-conf on-chain. But Lightning will be better suited to IRL purchases anyway, the infamous cup of coffee use-case. Cafes don't want to screw their customers over for the most part, they have to live with the consequences of that, so using Lightning in situations where you trust who you're buying from is the most suitable use case (and also matches the high transaction volume, and instant fund clearance Lightning achieves with the high transaction, instant fund clearance requirements of IRL businesses)

It's possible too that an improvement in the design of Lightning, or an alternative off-chain network design might be able to give us 100% trustless funds clearance like on-chain transactions do, but we'll have to wait to see how that pans out.