As far as I'm concerned, the merit of this babbling vial theory boils down to two considerations.
1. What exactly is one instructed to do (especially in that previous game) if the mod tells them they're supposed to babble? I haven't been in a role yet where I was told to babble and I don't remember that happening in a game I've played. (Well, Coler did get weird singing Al Jolson songs in the nude once. But that was normal for him. lol.) I've seen a town drunk that was killed right away. All that meant was he'd possibly "witness" something while impaired so his information was doutbful. I've also seen where someone was blackmailed by another where he had to vote someone specific. We've had various other spoiler roles too... assorted serial killers, renegades, vigilantes, etc.
If DD was babbling now, would she just post something not was true? Is it intended to be something self-incriminating? Or would she post something non-sensical? I don't remember if that vial was used in the badlands game or not (it not being one of my favorites) and I'm not going to have time to read another game today. If someone could answer this for me, I'd appreciate it.
2. Whether or not Pappy mentioned this just to mess with us. From what I've seen, Pappy seems to be most accurate with us when he tells us who died/didn't die, how, and by whom. We've also seen he does report when someone is turned. I think where he messes with us the most and is confusing/mysterious is while describing the new game format he's using for a new day. Example: Going into the badlands format, he hinted about blue mist on the horizon. Yet there was no blue mist come nightfall.
At this point, I'm discounting the babbling vial theory in DD's case because the case presented against her seems reasonable enough without it (IMO)... because I don't know if that's how a babbling role is manifested in someone's posting... because it seems a stretch for us to assume Pappy was trying to mislead there instead of clarify... because the fish/RAT code word theory was proved wrong... and because Pappy's comment is more simply explained by saying that was him telling us someone neglected to send him a PM or they told him they'd rather not use that vial.