Dear Professor Kapstein,
I thank you very much for sharing this interesting discussion from the archives of the Journal of the Royal Asiatic Society, 1906, to all. I also thank Victor Davella for sharing it to you.
As I see with the limited access, this discussion involves the discussion on a vārttika on Aṣṭādhyāyī (A) 2.2.6. There is no clue about the source text, both the scholars are referring to. One source could be the text of the Kāśikāvṛtti (KV). The printed text of the KV that they could have access to, could be, perhaps, the 1876 edition. This edition has this vārttika on A 2.2.6, indeed!
It is noteworthy however, that the Hyderabad edition of the KV does not have this vārttika in the main body of the text of the KV on A 2.2.6. Also the edition of the KV on A 2.2.6 published by me on the basis of 70 manuscripts does not have this vārttika in the main body of the text of the KV on A 2.2.6.
Interestingly, the manuscript which is amongst those which added this vārttika in the main body of the text of the KV on A 2.2.6, seems to be one of the sources of the 1876 edition.
with regards,