MESELF ,this is purely subjective,but I think part of the style of playing blues harp is bending notes.
I also think [and I live very close to Sliabh Luchra,and hear a lot of the music]that Sliabh Luchra,style of Irish Polkas requires a driving aggressive vigorous approach.which is suited by chordal or octave playing,Octave playing can be achieved by tongue blocking,chordal can be acheived either way.
Steve your playing of OCarolan,and the reels is very good,but you havent got it on the polkas or the out on the ocean set,you need to listen to Johhny o leary,or jackie daly.