Good thread. I suggest we collect specific scholarly quotes and acknowledged juristic rules that articulate what the burden of proof is in this case,
One well recognized principle that asserts the burden of proof is
البينة على من ادعى واليمين على من أنكر
"Clear evidence is upon whoever claimed and the oath is upon whoever denied."
That is, the claimant must furnish
clear evidence but all the defendant has to do is to swear that he did not commit the offense.
This way we would not be imposing an 'external' standard.
Ironically, those legal terms all came to the West from Islamic law! That reminds me of the word logrithm, which Arabs who do not know the origin of the word have translated it لوغارتم, a transliteration, not a translation, when the word came from the last name of the Muslim mathematician Al-Khawaarizmi
Here, I am going to mention what he (Nada) said about the burden of proof for establishing that abrogation has occurred in the Quran in general, which is usually done through citing 2:106 and 16:101.
...
مع الاحتمال يسقط الاستدلال
An alternative possibility precludes citing as evidence
That's a good one.
I would like to pin down these statements in a terminology that is accepted by Islamic scholars, and supported by rules that they themselves set.
We have plenty of that scattered all over the place in this forum. Much of it is in the individual cases and some is in the
Definition of Abrogation,
Inconsistencies,
Scholars opinions about abrogation topics.
We also have topics in the other forum,
Deduction Methods addressing various juristic definitions and principles made by the scholars many of which can be applied to the abrogation claim.