I wrote the spec to have human-readable components to it.
I may have missed it. The only human-readable components I could perceive would suffice to inform me that it was a proposed transaction, but would offer no idea what the transaction was. It looked more like a PGP message. I see no problem with a PGP message being un-human-readable, since that's the purpose of PGP. I don't think that virtue applies here.
...With arbitrary symbols/words in the format, it can lead to deceptive practices of giving people TxDPs that look like one thing to the eye, but turns out to encode something else...
Can you provide an example of what a deceptive one might look like? I suppose the comments could be deceptive, but that could be handled by eliminating or forbidding them.
The transaction block would only contain specific words that are defined by its spec, and only in the sequence permitted by the spec. Arbitrary words would only belong in comments, if allowed, where they would be ignored.
At a glance, one could read the transaction and quickly see what was proposed. They would see what is signed and unsigned.
Upon pasting it into their application, a user would see one of only a few possible responses:
1. This is not a well-formed transaction.
2. This is a transaction awaiting signatures. You can sign it, and then it will be complete and can be executed.
3. This is a transaction awaiting signatures. You can sign it, but it needs further signatures to be complete.
4. This is a transaction awaiting signatures. You do not have any of the keys it requires, and cannot sign it.
5. This transaction contains signatures that are not valid. The transaction may have been changed since it was signed. Remove the invalid signatures?
6. This transaction is complete but has not been submitted to the network. Submit it now?
7. This transaction is void because one or more of its funding sources has already been spent or redeemed.