So what you're saying, basically, is that the old wisdom of setting the cap iron very close to the cutting edge of the sharp (obviously) blade reduces or eliminates tearout. Alternatively, or in conjunction with setting the cap iron close, and turning to another old trick, i.e., doing tuning work on the upper face and lower leading edge of the cap iron helps the shavings curl up, or whatever, out of the mouth. What you seem to be saying is those plane maintenance and tuning techniques are 'influence' because they create 'influenced' shavings.
I'm not sure I've fully understood you, but I think I've got the gist of it. Thanks In essence, if a plane works effectively without causing tearout I've always thought of it as basically well tuned and set up. Slainte.
You've not looked close enough if you think of shavings curling up being the evidence,
as it's very much the opposite case,
and yes the closer the cap iron is, or indeed the steeper the leading edge of the cap iron is,
the more influence it will have.
The idea of having enough influence that it will work as it should, yet still as little as possible
for efficiently the work at hand.
To be experimenting with this without having a smoother or just another iron which you
know won't tearout is a bit risky though.
Grand if you're allright with scraping flat surfaces until then though, as the tearout won't be so deep, (should it be set just a smidgen closer)
FWIW, the no.5 1/2's cap iron is honed at (a conservative) 50 degrees
and the distance set from the edge is just under 1/32" (set any further away than this, will render it in-effective)
Then the no.4 smoother to get rid of the last bit of tearout,
cap honed the same angle, but for this plane, the cap iron is about 1/64" away from the edge.
And has more infulence which produces straighter shavings,
the straighter the shaving the less chance of tearing out.
and going back to the question at hand...
Obvious enough that this would render it impossible to utilize the cap iron with clipped corners,
and as Jacob said, camber is needed, more precice than many might suggest, but I'm not suggesting starting a sharpening thread about that.
That practice of clipping the corners is the worst offender in the list of three sure ways to fail
attempting to utilize the cap iron.
Tight mouths are up there as likely the most frequent offender.
and not having honed the cap steep enough being the third reason,
and most likely the case of folks unwilling to "devalue" their premium hand planes by doing such a thing.
FYI Cosman might suggest the same advice, should one never have listened to him,
and seen straight shavings.
He's set up his plane to be intentionally elusive, as he sells the tools.
No surety can be had if doing such, as can be seen on his videos...
should one have enough determination or curiosity they would see this, i.e look up back bevels,
he's not shy of showing this, but has so many videos to obscure matters,
that it doesn't show up the shortcomings of his luring yet profitable plane setup.
Still, better than denouncing the use of such in its entirety, which seems to me, possibly to be impressive and unexpected tactical error playing that game, seeing as anyone and everyone has access to video production these days.
Tom