I changed my perspective on keys after meeting someone with absolute pitch. When I play something “in the wrong key”, she complains!
Here’s something you can do with an Eflat whistle:
… is it my imagination, or does he half-stop the END of the whistle occaisionally with his right-hand little finger? If so, maybe he’s using an Eb because he can’t quite reach with a D whistle … or was that the point of the link 
I didn’t watch this vid … But yes, I’ve seen Brian sometimes half-stop the end a semitone below the bell tone. Obviously easier on an Eb than D, but he has quite large hands anyway.
You don’t have to be insisting on a ‘correct’ key to feel that key signatures make a difference. Don’t you find, if you play the same tune, on the same D whistle, in B minor or A minor, that it makes a difference to the sound?
Here’s Scott Skinner’s take on different keys - presumably on the same fiddle :-
C - bold and piercing
A min - sad and plaintive
G - plenty of body
E min - sterile, thin
D - splendid body
B min - rather sad
A - the fiddle key
F min - exquisitely harrowing
E - brilliant but lacking in body
B flat - velvet, very rich and fine
E flat & C min - weird, fascinating and beautifully sad
These judgments will of course have a lot to do with his particular instrument. I would strongly disagree with his feelings about E min and C, but they may rest on the resonances of his fiddle played in his style.
Last weekend at the RSCDS workshop, we played a set of reels where the last tune was in E; the leader asked how we liked it, and someone said ‘nice tune, but do we have to play it in that key?’ to which the answer was yes, the brightness of the key (following the 3rd tune in A) helps lift the dancers for the last time through the dance.
So the reason for playing it in E was not ‘that’s its original key’ (though it was), but ‘it works in that key; it does a job’.
My original question on this thread was really ‘what works on an E flat whistle?’ rather than ‘what’s correct on an E flat whistle?’
‘Anything works’ is of course a fair answer on one level, but not terribly illuminating.
The question as you posed it was:
and in your opening statement you clearly put forward you don’t perceive the relevant keys of much use in ‘folk music’. You then quote three Carolan tunes that you apparently think are written and therefore correct in a key suitable for thee e flat whistle.
Suggesting you expand your thinking towards a less tied to the perceived ‘correct’ would seem enlightening enough for you to deal with for starters.
Maybe you retrospectively changed the question, maybe your opening was badly phrased, maybe both. Consider that one for a minute or two.
makes you wonder what Brid could possibly be thinking of with all those odd whistles…
http://www.bridodonohue.com/tobar_main.php
Singers must love having her around. 
But seriously, I’ve known enough people with perfect pitch who can transcribe on the fly and not complain about the key to think she’s the exception and perhaps forming your own musical philosophy independent of her ears (gifted though they may be) would do you better in the long run.
makes you wonder what Brid could possibly be thinking of with all those odd whistles…
The ‘odd’ Sindt in the picture is mine, she had that on loan for the recording. I got her one (when John accidentally sent me a D instead of the B I had ordered. He sent the B to replace it anyway) by the time the recording was about done.
The blue gen’s head in the pic is really bent by the way. That’s not a by product of the photography (but I would say that wouldn’t I?).
Just noting that the “Gallery” link on Brid’s website is broken. 
She can transcribe and adjust (she plays Boehm flute semi-professionally). It’s just that she’s aware of the key of the original recordings of songs we play. As I understand, changing the key, to a person with absolute pitch, sounds somewhat like changing the melody instrument would sound to the rest of us - clearly the same tune, but different. Not something to be done without some kind of artistic justification.
What some comment about “What Do You Do With a Drunken Sailor?” or some other cheap remark? Chiff Board members don’t resort to those kinds of things.
-… the Captain’s daughter, early in the morning.
Ok, now the songs stuck in my mind. 
I got to go play it out.