Greetings @Mat,
I suppose we could go on diverging for ever. However, it is not so much about saṅkhāra that we should talk about, but duality.
Then again, let’s try to cover both.
Here, I am talking about saṅkhāra as the active force; not the things produced by them.
Saṅkhāra (Skt: saṃkara,) is not a Vedic word.
The meaning of saṅkhāra has therefore to be found conceptually; neither lexicographically or etymologically, as far as influenced are concerned.
For instance, we can equate it with this instance in the ŚBr:
1:6:3:23. Twofold, verily, is this, there is no third: to wit, the moist and the dry; and what is dry, that relates to Agni; and what is moist, that relates to Soma. But (it may be objected) if this is twofold only, why then this manifold performance:–the two butter-portions for Agni and Soma, the low-voiced offering to Agni and Soma, and the rice-cake for Agni and Soma,–when by means of any one of these he obtains all, why then this manifold performance? [The answer to this objection is that] so manifold is the power, the generative force of Agni and Soma.
Dvayaṃ vā idaṃ na tṛtīyamasti | ārdraṃ caiva śuṣkaṃ ca yacuṣkaṃ tadāgneyaṃ yadārdraṃ tatsaumyamatha yadidaṃ dvayamevāpya kimetāvatkriyata ityagnīṣomayorevājyabhāgāvagnīṣomayorupāṃśuyājo 'gnīṣomayoḥ puroḍāśo yadata ekatamenaivedaṃ sarvamāpnotyatha kimetāvatkriyata ityagnīṣomayorhaivaitāvatī vibhūtiḥ prajātiḥ.
It is the duality (dvaya,) that is empowering the generative force - the active force - (think about the vital air - Assāsa/Passāsā).
That active force, that took the name of saṃkara (saṃkṛ,) later on in late Vedic (post Buddhist) time, took also the meaning of confusion, and of pollution.
Was it the same conception in Buddhism? - A generative, confusing & polluting force?
Are the impermanence of formations (the things produced by this active force,) dependent on the nature of the force itself?
How could we go further than this litany of common grounds served by Thanissaro & C°, or the Abhidammic crowd? - Déjà vu (and quite dubious for the latter).
It could be interesting to talk about all that - But here again, it is duality that concerns us. And more precisely, the duality of consciousness.
Note that I am not going to complain about diverging a bit, if this is interesting. And it is.
Sleep well, dream well; and tell me about that tomorrow.
Metta
suci