Mr Donald's motives are quite clear. He claims that every Sinhala character shape needs an individual "code point", and has applied for a patent for this "invention". With Sinhala Unicode becoming mainstream, avenues for making money with his pending patent are going thin.
So he is doing what any desperate human being (or animal for that matter) would do; try everything to remove the "opponent".
One of the examples Mr Donald always uses is the absence of character "du" in the Sinhala Unicode codepage.
Of course he conveniently forgets to mention that "da" and "papilla" are in fact available. Well, it requires a bit of brains to put them together. ;-)
Mr Donald, there are lots of missing characters in the Sinhala Hodiya (alphabet), including your infamous "du", let alone "yansaya" and "rakaransaya". If you love the Sinhala language so much as you claim, please start a campaign to "fix" Hodiya!
I have previously pointed out this similarity between Hodiya and Sinhala Unicode, and why "du" + "papilla" is as good as "du". This blog post discusses technicalities in detail including the matter of "yansaya" and "rakaransaya".
Unfortunately for Mr Donald, his "opponent", namely Sinhala Unicode, is growing stronger day by day. Implementations are maturing, more standards compliant fonts are beginning to appear, and as I wrote earlier, more web sites and blogs are now Unicode compliant (e.g.: Sinhala Bloggers, Sinhala Wikipedia, Sinhala Blogs and of course our own Sinhala GNU/Linux).