I don't want to play Irish music on an EC like an AC. What I wish I could have done was to play the fiddle. That didn't happen, so I guess I live with second best and what worked with the muddle that is my mind....Over the years I have come to love it almost as much as I envy fiddle players .
As an Irishman, and thus one who grew up with the entire spectrum of Irish music - of which so-called ITM is a stylised version of just a small segment - I can relate to that.
Irish dance music is not concertina music, certainly not Anglo concertina music. It is a body of melodic material, with a range of rhythms matching the indigenous dances. The traditional way of playing this material has emerged because of the necessity for a solo fiddler or piper to provide the music for dances in times past. The decorations are there to provide the musical interest and rhythmic support that in other traditions come from accompanying instruments. Later, fluters found ways to realise this playing tradition on their instrument, too.
Fluting, fiddling and piping are all older in Ireland than AC playing. When the AC came along, players looked for ways to adapt to the tradition, as the fluters had done before them.
One thing that fiddle, flute and pipes do NOT have is a necessity to change bellows direction! The fiddler is free to change his bow direction when he wants to (within reason, like an EC player his bellows); the bellows of the pipes are independent of the flow of the music; and the flute has only one airflow direction that has to be interrupted to take a breath.
Each has its limitations, too: the fiddle can't sound more than 2 notes at once; the flute can only sound one, and needs pauses for breath; and the pipes have no dynamics and their sound cannot be interrupted.
The standard C/G Anglo has a decisive disadvantage in this fiddle-determined music, which is often in D or A, which is alleviated by the sparseness of harmonies that was, thankfully, part of the tradition before the concertina arrived. So the AC can find, and has found, its entree.
But why must the EC come in by the same door? The AC does not sound like the traditional pipes, so why should the EC sound like the meanwhile traditional AC? The clips of reels on the EC linked to from this thread remided me very much of uillean pipes - the most traditional dance-music sound you could get. Like the pipes, the EC gets its emphasis from the fingering and the sparse harmonies. If you want to dock on to ITM with your EC, it would seem to me more logical to emulate the pipes than the AC.
Of course, ITM , like OTM in the US, is a vested interest of AC teachers and AC builders, among others, so they have an interest in regulation. And apparently, in their opinion, a concertina that wants to be ITM has to sound like an AC.