There is a web site with a fairly heavy treatment of Irish Modes and the “D” Tin Whistle at:
http://www.geocities.com/novairishsession/modes/modes.html
Perhaps this site is known here, but I haven’t run across it before.
Fairly heavy treatment? 
I agree it could have been a bit simpler - I can’t see why you need to bother your head with exotica such as the Lydian, Phrygian and Locrian modes in a page dealing with Irish music and the whistle.
The thing to remember is that modes provide only a partial answer to the structural mysteries of Irish music. Gapped scales and “complex tonalities”, both of which are very frequent, go beyond the question of modes.
It’s all a very good subject for a doctoral thesis for some young, carefree budding ethnomusicologist. (I can be ruled out on all three counts.)
I thought all the whistle tabulature for this mixolydian scale or that was pretty heavy…
In a way I feel this thread belongs in the Poststructural Tinwhistle Forum, but now that we are here.
A great player once made a remark to me that I felt related to modes on the D whistle in a different, practical way. The thing about modal and especially gapped scales is that they will sit on a whistle in several keys. And yet, this player told me, it makes a difference in the sound and the feel: If you play for instance the Yellow Wattle on a D whistle it has a special quality that it loses when you play it on a C-whistle (easy enough, though you have to contend with G# in the B-part (try xxoxxo).
Actually, it’s an F#, not a G#, if you know what I mean.