If whatever happened 25,50 or 100 years ago didn't matter, then why even have this discussion at all? I believe one influence on guitar playing in sessiúns was Tish Richardson(R.I.P) who played with the Boys of the Lough. He learned his playing from a Northumbrian player I think was called Willie Johnson learned how to play from listening to Django Reinhardt on a short wave radio.

At most the sessiúins I go to, people agree that one guitar or bouzouki is enough. I have heard some players who do well with a strong rythymn and a minimum of chord changes like Mick Moloney and others who do some great jazz-influenced chord changes like John Doyle.

I much prefer Irish songs unaccompanied. Guitar accompaniment is much better suited to Bluegrass or Country music.