Does anyone know what it in the nature of a hornpipe that resists being played as a reel? I don’t think it can be done, you just can’t play it without leaning on every other note. It’s as though there’s something in the dna of a hornpipe that insists that it only be played as such.
This has been a topic before - and I personally get what you’re saying. However, people DO play hornpipes as reels, either because they can and want to mix it up, or they need another reel for the dancers and the hornpipe that just popped out can be made to do with a little tweaking, or maybe they just learned a tune that way and don’t know any differently.
Me, when I hear a hornpipe played as a reel, it always sticks out because there’s a particular structure that is signature to typical hornpipes, quite distinct from that of the typical reel, and that structure endures no matter how you play it. In that sense, to me it isn’t really a reel at all (and to me, ever); it’s just being played as if it were one. OTOH, if it’s played like a reel and, moreover, people are happily dancing reels to it, then functionally what you have going there is, for all momentary practical purposes, a reel.
So … it’s not a reel … unless it is!
Exactly. 
Well, thanks for putting us all right on that one. I’ll know now.
I but observe.
Personally, I prefer keeping reels and hornpipes distinct so they may be celebrated to the fullest extent of their own particular intended glories, but that is perhaps over-rigid of me, a pedant’s stance being possible testament to traces of still-lingering n00bosity.
Although I just call it personal taste. 