...I feel kinda uncomfortable arguing against someone with an account as much bigger than mine than yours is, since I've definitely seen a lot of people use their larger accounts to target smaller ones like mine (a flat earther went out of their way to crush one science aficionado's account a couple months back), but from what I can tell from your history, you seem pretty cool.
Anyhow:
There's exactly zero evidence of the Younger Dryas impactor that has stood up to peer review. Zip. Zilch. Nada.
There are no ash deposits. Minor volcanoes leave ash deposits, so a meteor or comet sure as hell would. This one didn't.
If the impactor had been cushioned by the ice, it would have melted the ice. That in turn would have led to flooding comparable to or greater than the Missoula floods, and rather more recent- and trust me, we would have noticed that.
The supposed lonsdaelite (nanodiamonds formed from the impact)? Not only have they never been found by anyone else, other scientists have identified the ones by the comet proponents as actually being polycrystalline aggregates of graphene and graphane, which are definitely not related to impact.
When we actually look at the graph, though, we see that around that time we were in a highly variable period in the Quaternary glaciation cycle. That brief resurgence of glaciation? It's well within our expected deviation. It simply doesn't need a comet to explain it.A comet or meteor would not cause a spike in temperatures. Instead, it would cause a drop in temperatures. (I'm assuming that's a typo on your part, though- happens to me all the time, especially on my phone.) 
You ask me to challenge the orthodoxy- except in geology, we literally just overthrew the orthodoxy a few decades ago. As a science we're just now starting to gather our feet under us after the plate tectonics revolution. It was one of the biggest upheavals in the history of any science, and literally nothing in geology survived without being put through a crucible to stress test it. Calling for me to challenge the orthodoxy in geology right now is kinda like demanding that America demand independence from England in 1790.
I admit I'm no geology student (I studied economics), but I'm seriously confused now. We have these 4 papers alone in the last 2 years that confirm remnants of a high impact event 12,800 years ago and you're saying it's all bogus without providing any peer reviewed sources. I find it extremely odd that geologists could be finding the same remnants at the exact same time period across 4 continents and geologists claim it's "never been found by anyone else" (except for multiple independent teams).
Help me learn. Please look at these sources and let me know what is wrong about them:
https://scholar.google.com/scholar?q=Anronikov,%20A.%20V.,%20I.%20E.%20Andronikova,%20C.%20W.%20Loehn,%20B.%20Lafuente,%20J.%20A.%20M.%20Ballenger,%20G.%20T.%20Crawford,%20D.%20S.%20Lauretta,%20Implications%20from%20chemical,%20structural%20and%20mineralogical%20studies%20of%20magnetic%20microspherules%20from%20around%20the%20lower%20Younger%20Dryas%20boundary%20(New%20Mexico,%20USA).%20Geogra%EF%AC%81ska%20Annaler:%20Series%20A,%20Physical%20Geography%2098:1%E2%80%9321%20(2016).
https://scholar.google.com/scholar?q=Mahaney,%20W.C.;%20Somelar,%20Peeter;%20Dirszowsky,%20Randy%20W.;%20Kelleher,%20Brian;%20Pentlavalli,%20Prasanna;%20McLaughlin,%20Shane;%20Kulakova,%20Anna%20N.;%20Jordan,%20Sean;%20Pulleyblank,%20Coren;%20West,%20Allen;%20Allen,%20Christopher%20C.R.,%20(2016)%20A%20microbial%20link%20to%20weathering%20of%20postglacial%20rocks%20and%20sediments,%20Mt.%20Viso%20area,%20Western%20Alps,%20demonstrated%20through%20analysis%20of%20a%20soil/paleosol%20bio/chronosequence.%20J%20of%20Geology%20(in%20press).
https://scholar.google.com/scholar?q=Holliday%20V.,%20Surovell%20T.,%20Johnson%20E.%20(2016)%20A%20Blind%20Test%20of%20the%20Younger%20Dryas%20Impact%20Hypothesis.%20PLoS%20ONE%2011(7):%20e0155470.%20doi:10.1371/journal.pone.0155470
https://scholar.google.com/scholar?q=Kennett,%20James%20P.;%20Kennett,%20Douglas%20J.;%20Culleton,%20Brendan%20J.;%20Emili%20Aura%20Tortosa,%20J.;%20Bischoff,%20James%20L.;%20Bunch,%20Ted%20E.;%20Daniel,%20I.%20Randolph,%20Jr.;%20Erlandson,%20Jon%20M.;%20Ferraro,%20David;%20Firestone,%20Richard%20B.;%20Goodyear,%20Albert%20C.;%20Israde-Alc%C3%A1ntara,%20Isabel;%20Johnson,%20John%20R.;%20Jord%C3%A1%20Pardo,%20Jes%C3%BAs%20F.;%20Kimbel,%20David%20R.;%20LeCompte,%20Malcolm%20A.;%20Lopinot,%20Neal%20H.;%20Mahaney,%20William%20C.;%20Moore,%20Andrew%20M.T.;%20Moore,%20Christopher%20R.;%20Ray,%20Jack%20H.;%20Stafford,%20Thomas%20W.,%20Jr.;%20Barnett%20Tankersley,%20Kenneth;%20Wittke,%20James%20H.;%20Wolbach,%20Wendy%20S.;%20West,%20Allen.,%20(2015)%20Bayesian%20chronological%20analyses%20consistent%20with%20synchronous%20age%20of%2012,835%E2%80%9312,735%20Cal%20B.P.%20for%20Younger%20Dryas%20boundary%20on%20four%20continents.%20Proc%20Natl%20Acad%20Sci%20U%20S%20A%202015%20Aug%2027;112:32%20E4344-53.