Affected by Luck STAT?

Well, I don't doubt you (or I'm denying the doubt).

You do raise a good point about Ruairi and Cessair's Heart. They have 1490 Luck (minus the 10 from character creation) and yet their lucky finish rate seems to be the same as a player with 100 or 0 luck.
As for Lucky Gather, the only NPC with high luck who actually gathers is Shakespeare, I think. The one where he mines flint. Sadly, he only had 500ish Luck, and IIRC the mission clears instantly once the animation completes...

Have those JP people done tests on other things and if they did were those proven to be accurate?

I also want to point out the -10 luck only affects critical %. Everything else appears to leave Luck unscaled and has no known cap on luck-based effects.

It... doesn't? Now I'm really more confused about that -10 aspect...

-10 only applies to critical calculation. What's there to not understand? Luck appears to be unscaled when calculating bonus gathers.

I also want to word this:
Luck1あたりラッキーフィニッシュ発生率0.005倍ずつ上昇

To something like every 1 luck adds .005% chance of a lucky finish...that's is really minuscule...and just awkward as hell to say.

I meant overall. 10 is nonexistent so shouldn't the subtraction be universal to everything?

1 Luck = .005% increased chance. 1,500 Luck = 7.5% increased chance. That sounds awfully doubtful...

Apparently not if it's using a whole number to begin with. Luck a strange stat to tackle when getting everything down outside of critical calculations :c

Large math aside, 1/66 + .075 isn't exactly much of an improvement to begin with.

I hate this game when it comes to incredibly weird and ridiculous calculations.

(# / 0 Luck) = Undefined
1 / Undefined = ?!?!!?!?!?!?!?!?!? THIS IS MADNESS

In what game is anything divided by 0 not undefined?

Well at least we know why it comes up as 0 luck = No lucky gathers.