Therefore I cannot know whether my personal details are to be signed by a CA until after the event has taken place. This is a concern. If you are saying that this is not a correct description, and that the message is communicated directly between user and merchant using SSL, then please be more explicit in confirming this.
If you're saying that the non-repudiative proof is the only information signed by the CA, then please be more explicit in confirming this.
The only signed data is the request to pay, which is signed by the merchant (when used, it's optional), and the merchants own credentials which are part of a certificate he sends (if he is doing the optional signing).
There we are, that's better! If you want to answer the questions I have asked you, but in the form of a response to some other part of the dialog, then I can add the clarity myself by bringing the two together via cut and paste. It makes the conversation appear less intransigent to those that are following it. Why don't you want to answer the question directly? Why is it necessary to use personal sleights in your indirect answer?
The notional concern that you are talking about is that of generating a proof that a given payment request was instantiated at the users end, such that a webmerchant cannot be accused of sending unsolicited requests to pay.
No. I'm not talking about that at all.
Nothing stops you from sending unsolicited requests to pay.
A payment request is like an invoice, it forms an agreement "I'll send you the things listed on the payment request, if you pay this amount to these scriptpubkeys." the request can be signed so that you known who its from, and the signature is non-reputable so that if they don't make good on the deal you can show someone the payment request (and the transactions in the blockchain) as evidence that an agreement existed and you kept up your side of the deal.
My apologies, but you were incomplete in the way that you described your non-repudiative case, the subject of the repudiation was ambiguous. The above more than satisfys a complete description.
"Word salad" is an expression that's used to describe sentences that are logically and/or grammatically obtuse. My sentence made sense, but didn't describe a situation accurately. A little less haughty, please, you are being impolite.