Transliteration of the Letter ' r ' In Tamil Language

I have been observing for quite long,that the use of  the letter 'r ' in Tamil for some words in Tamil is sightly different as to what I have known from young.The Internet and Google transcription provides a platform completely free to type and share Tamil Documents and Papers.I have come across many websites and blogs where this ' r ' is typed differently.As for me personally writing a Tamil Novel (possibly in future ), the typed version of this letter ' r ' is different from the printed one that is available as Books.There is a wide variance and many people well versed in Tamil language find this difference to be a little annoying.They see words that completely appear different  although the meaning does not differ much.Surprisingly this can be found only in the letter ' r ' and not in any other letter of from the remaining 17 Tamil consonants.( Tamil Alphabet has 18 consonants, 12 vowels and one character) 

One can notice the difference of  ' r ' (ir , irr) from the above image.During my chat with a few Tamil Blogger in Face Book,I asked them the same question.Though they understood , they could not come with a proper answer and in fact many feel comfortable with  the present Transliterated ' r ' for their blogging.

The letter ' r ' becomes Tamil ' ir' / 'irr' and the letter ' R ' becomes 'itir' / 'itirr' when transliterated .Also from the above picture, you can clearly notice that this happens only for the small letter 'r' .

Recently I came across a paper 'The history of R'  from  the Journal of the American Oriental Society   where in a similar doubt was arised by the use of 'R' in Tamil Linguistics.Though understanding this concept was beyond my knowledge of Linguistics ,I am embedding the same for convince 

Journal of the American Oriental Society © 1937 American Oriental Society

PS : Tamil has always been a powerful and interesting language ..The authors of the Unicode fonts and TSCII fonts have come up with a way of typing Tamil easily in Computer and Mobile Applications.As a ardent lover of Tamil , I have highlighted what I felt was different in using the letter 'R' or 'r' than what I know it when I grew up. 

The purpose of this post is to highlight my own opinion for Tamil Transliteration of the letter 'R' or 'r'Kindly share your thoughts if you feel I am right or wrong.