There's a bunch of "should" in this argument. I won't debate whether it should have liability, but I'll point out that no matter how it ought to be, according the law of the land at least in EU any payment service provider inavoidably has liability in certain cases e.g. when your account has been hacked; if they are unable to reverse a transaction that wasn't authorised by me but by someone else, well, that's their problem, they still have to compensate the consumer above a self-risk of 50 Eur.
The original article mentions UK Consumer Credit Act which IMHO is not appropriate (its scope is limited to credit relations, and the protections of that act generally exclude both debit cards and most e-money systems including Libra), so the scope for potential payment service provider involvement in disputes between buyer and seller is narrower than that - and probably closer to your "should" statement than the arguments of the original article.
However, it can't be a fully neutral platform distancing itself from all liability. It is illegal to "simply" offer payment services without incurring any liability for misuse of them, breaching AML/KYC regulations, etc. Facebook has not yet (as far as I know) stated what exact legal structure they'll use for compliance with the legal requirements, so I can't comment on that, but they did make statements that Libracoin will comply with the EU regulations so I presume that some legal entity regarding Libracoin (possibly co-owned by the consortium members, or possibly multiple entities) will (have to) be a licensed payment service provider in EU, and similarly (it's usually done with separate legal entities) in other major jurisdictions.
Technical structures that "just happen" such as Bitcoin can ignore regulations but any person or organization that wants to offer services using these technical structures is fully liable for meeting all the legal requirements - and if the technical structure makes impossible to do something, they're still fully responsible for any consequences of not achieving the impossible thing; if they don't want the liability, they're free to not use that technical structure and not use/offer/advertise anything with it.
This thread was originally about the social and technical issues of scams in the context of irreversible ledgers, not legal liability. As far as that goes I am in full agreement with you: Facebook and other Libra consortium members are likely to face quite a bit of legal heat from various jurisdictions desiring them to block or reverse transactions and willing to hold them accountable for others' actions on the network. In my opinion the only sane way to introduce something like Libra would have been to give up control entirely, along with the ties to fiat currencies, and make it a permissionless, decentralized system like Bitcoin. Exchanges in a decentralized system have various regulations applied to them but in the end they aren't inherently in the position of transmitting money on behalf of their users; nor are they strictly necessary for the network to function. Libra, on the other hand, will be seen as a payment system controlled by Facebook and the other consortium members, and Facebook itself as a money transmitter, not a mere buyer and seller of coins.
Personally I find it much more interesting and productive to debate what the law ought to be rather than what it is, but as a practical matter Facebook will obviously need to take the various injustices of the jurisdictions in which they intend to operate into account—and the centralized design of Libra doesn't seem very well suited to deal with that reality.
The original article mentions UK Consumer Credit Act which IMHO is not appropriate (its scope is limited to credit relations, and the protections of that act generally exclude both debit cards and most e-money systems including Libra), so the scope for potential payment service provider involvement in disputes between buyer and seller is narrower than that - and probably closer to your "should" statement than the arguments of the original article.
However, it can't be a fully neutral platform distancing itself from all liability. It is illegal to "simply" offer payment services without incurring any liability for misuse of them, breaching AML/KYC regulations, etc. Facebook has not yet (as far as I know) stated what exact legal structure they'll use for compliance with the legal requirements, so I can't comment on that, but they did make statements that Libracoin will comply with the EU regulations so I presume that some legal entity regarding Libracoin (possibly co-owned by the consortium members, or possibly multiple entities) will (have to) be a licensed payment service provider in EU, and similarly (it's usually done with separate legal entities) in other major jurisdictions.
Technical structures that "just happen" such as Bitcoin can ignore regulations but any person or organization that wants to offer services using these technical structures is fully liable for meeting all the legal requirements - and if the technical structure makes impossible to do something, they're still fully responsible for any consequences of not achieving the impossible thing; if they don't want the liability, they're free to not use that technical structure and not use/offer/advertise anything with it.