Did Ralphie really start the fire in the barn that killed Pie-o-mie

Chase wrote the scene with the intention that Ralphie had done it. But when they were shooting the final confrontation he told Joey Pants that Ralphie didn't do it. So now you have an actor portraying an innocent man being wrongly accused, but saying and doing everything a guilty man would do. This creates the confusion over the truth that still exist today.

Its a plot hole. No one knows

Yes, David Chase confirmed it on The Sopranos podcast last week.

My take is that Tony killed Ralph because of both the death of Tracee and the horse.

Tony had pent up feelings about what Ralph did to Tracee and when the horse died he both suspected and wanted to believe Ralph did it as an excuse/motivation to exact revenge, for both.

The line about "beautiful creature" was about the horse but it could, and probably did, have a double meaning for Tony. Unspecified and ambiguous words spoken during a fit of murderous rage.

Yes he did. From the horse’s mouth: https://youtu.be/mxxpS9sCCLI?t=1627

No, I never thought Ralph did it given how furious he was in his denial - contrasted with flippantly trying to pass his murder of Tracee off with "eh she slipped and fell...I don't know..."

Yet he said everything to trigger Tony regardless. Another example of the absolutely brilliant writing of the series.

The actor says he didn't:


https://youtu.be/3DHy4xOLucM?si=sAesXS4WCbLhee1c

I always thought he had and admitted to it when Tony pressed him.
Maybe I've remembered wrong, or that i interpreted the part where he shouts "who cares" as an admission - if nothing else, he'd stopped denying it when he said this.
Anyway, what i was going to add in this thread is that, earlier in Season 4, Tony was present when Ralph speaks to Johnny Sack and attempts to deny that he'd made the joke about his wife.
(1) similarly, when he says "if that's what it takes" (re apologizing for the comment), Tony damn near face-palms as he knows Johnny will take this as an admission of guilt. Which it is.
(2) and more crucially, Tony had seen and heard first hand Ralph lying and denying something he's really done, so knows what 'tells' to look and listen out for when he confronts him about the horse.