Dear Christopher,
The issue we are discussing needs a philological solution. What you have done in your most recent post is to make a philosophical argument, and a comparative-philosophical argument at that (basing yourself on where Abhinava or his school differs from other Indian philosophers or their schools).
You write: "vedha can indeed mean transmute ... The first is denoted by vidh-, permeate, infuse, but also transmute":
We need at least one passage, preferably in a similar context, in which it can be shown that it will not suffice to take vedha and other derivates of vidh/vyadh in the sense 'pierce, penetrate' etc. or 'infuse, permeate' etc. -- that we will be forced to associate the sense 'transmute, transform, alter, change' etc. Passages speaking of 'transmuting' as an outcome or a stage coming after vedha do not establish that vedha itself has acquired the meaning 'transmuting'.
You write: "the second, abhini+viś, immerse completely (now dehādi have become like gold) ..."
Here again, why we must/should go beyond the well=attested meaning of abhi+ni-vi;s, 'enter front and centre, establish oneself within, take hold, cling far' is not clear (cf. puurva.m hy apavaadaa abhinivi;sante, pa;scaad upasargaa.h in Pata;njali's Vyaakara.na-mahaabhaa.sya; the occurrences of abhinive;sa and abhinivi.s.ta in several texts). In some contexts one can perhaps extend these meanings to 'to be committed to, to be biased, to have one's mind made up,' but extending it to 'to immerse' seems too great a stretch. Note also that if that were the meaning, a locative would have taken the place of the instrumental sa.mvid-rasena.
Even if you succeed in overcoming the preceding philological difficulties, you will have to contend with the opposing evidence I have cited in which pure gold is clearly spoken of as the outcome and as becoming liquid as it were.
Clarification: I do not deny that there are passages which speak of disappearance of gold in mercury (perhaps in other substances as well). The question is whether they match the details in:
yadā tu parāmṛṣṭa-nityatva-vyāpitvādi-dharmakaiśvarya-ghanātmanā ahambhāva-siddharasena śūnyādi-deha-dhātv-antaṃ vidhyate yena prameyatvāt tat cyavata iva, tadā turyadaśā;
yadāpi viddho 'sau prāṇa-dehādi-dhātuḥ saṃvid-rasena abhiniviṣṭo ’tyantaṃ kanaka-dhātur iva jīrṇaḥ kriyate yena sa druta-rasa iva ābhāti kevalaṃ tat-saṃskāraḥ, tadāpi turyātīta-daśā sā bhavati.
(Your earlier translation preserved here just for my reference: "'But when the [layers of limited selfhood] from Void to the physical body are penetrated by the “alchemical elixir” that is the (true) I-sense—replete with the sovereignty of the qualities of eternality, all-pervasiveness, etc. which are cognized [as aspects of that I], by which their objectivity falls away as it were, then it is the Fourth State. When, further, these elements of prāṇa, body, etc., penetrated by the elixir of Consciousness, are completely immersed [in it], they are “matured” like the element of gold . . .'(?)"
Best wishes.
a.a.