Oh thanks, my bad, I’ve fixed it now.
Yes, it seems Netti is the form preferred by the Mahasangiti edition. It uses the title Nettipāḷi, but Nettippakaraṇa is found nowhere.
The BJT edition has Nettippakaraṇa for the title, and adds Nettippakaraṇaṃ niṭṭhitaṃ. in the colophon. The Mahasangiti has no “nitthitam” tag.
Interestingly, the VRI edition, on which the Mahasangiti is based, uses Nettippakaraṇapāḷi in the title and Nettippakaraṇaṃ niṭṭhitaṃ. at the end, like the BJT. The commentary also has Nettippakaraṇa.
The PTS edition mentions that it is known as Netti, Nettippakaraṇa, or “Netti-gandha” (? Nettigantha?). It cites a number of references in commentaries and Tika to the name Netti. The manuscripts themselves, of course, didn’t have titles. At the end of the PTS edition, it cites some variants as to the colophon, but does not say that any editions lacked the colophon entirely.
There must be some reason why the Mahasangiti made this choice. It’s noteworthy that the last line of the text refers to itself as netti:
Ettāvatā samattā netti yā āyasmatā mahākaccāyanena bhāsitā bhagavatā anumoditā mūlasaṅgītiyaṁ saṅgītāti.
The mainline text for the Mahasangiti edition is the 1st printed edition from the 6th council; perhaps this reading comes from there.
The VRI, BJT and others are all based on the 2nd edition. According to the Mahasangiti folks, this was in fact the 5th council edition; Burma had been through an upheaval and the printer used the wrong one. So all subsequent editions of the “6th” council are in fact “5th” council. Of course they are very similar. I can’t verify that this is true, but it would be interesting to check this detail against the 1st edition of the Burmese script 6th Council. But they are very rare!