So, the oracle has spoken!
All we need now is a virgin from the Greek Isles to reiterate the pronouncement.
All because CMLover correctly pointed out that
be assured that the phonetic rules 'mahakavi' is quoting are not sanctified by the original grammatical treatises (tolkaapiyam / nannool). There are modern grammar books written by some tamils (Singaporeans..) who cite phonetic rules which though logical are not necessarily authoritative. In fact ruling out 'ch' at the beginning of the word is an atrocity not found in other parts of TN except at Tanjore/chennai (or is it sennai ). Just like english Tamil has developed independantly in all parts of TN (in the world now-a-days) and hence there are no real phonetic rules to be strictly adhered!
I checked out the Tholkappiyam (by M. Ramalingam and Bhageerathan) and there is NO reference to change in sounds depending on location of a letter.
Think about it: how could a book talk about modification of "ch" into "s" when there was no symbol for "s" at the time the book was written?
Thus, there are also no rules about 'k' becoming 'g', 't' becoming 'd', 'p' becoming 'b', etc.
If anyone decides to quote ancient grammar in support of their contention, I can tell you it is not there in Tholkappiyam, the oldest extant Tamil grammar.
Tamil has evolved since Tholkappiyam. But any talk about sounds being modified to assume sounds used in Sanskrit (such as s, S, sh, j, h, g, b, d, D, etc.) could happen only after the introduction of those letters into Tamil, which can be dated by experts. It certainly does not date back to Tholkappiyam, Nannool, etc.