Thehe.

You're not wrong of course, I only mentioned it because sometimes I get the impression that the number 556 is thought to be
the breakpoint. Anyway, I think that the worst case scenario would be Baal (lvl 95) dropping a qlvl 39 item, which would need 551 MF to guarantee unique quality, so I don't think you'd ever need more than that amount for act bosses on Hell. But exceeding the breakpoint for unique items won't hurt your chances of course, so that's fine. If you're looking specifically for Set items however, you're better off not going past the breakpoint by too much as that would increase the Rare & Unique chances. But yeah, still nitpicking over here.
Btw, I think it should be fair to say that the qlvl is subtracted from
ilvl (and not necessarily mlvl), because containers use the same item drop function. But afaik there are no containers that give you that bonus that champions & unique monsters give, so it's probably not worth it to pop chests while wearing a lot of MF.
It was interesting to see btw that in this item drop function, if the source/target is a monster, then there's actually a check to see if that monster itself has any MF, which is then added to yours. And if the monster has an "owner" (like a Minion having a unique monster as owner), then the MF of that owner is added as well. Any clue what this might be about? Do some monsters spawn with items that can have MF? The only monsters I can think of don't drop items when killed (like Ancients, Valkyrie & those Shadows from the Assassin). The monsters I debugged all had 0 MF, and I'm not sure where to look to find out what this is about. I know it's not the "spawnpctbonus" from monstats.txt.
Interesting that the rlvl determination works that simply. I assumed that they had something overly complex in place that does a bunch of multiplications and divisions. :>
Edit: It looks like for crafts it is indeed 10+(3*random_affixes)+highest_affix_rlvl. This can be overwritten if the rlvl of the item itself is higher, or by +skill bonuses on the item (there are 10 stats checked specifically, I suppose these are those automod stats from Wands, Staves, Bows, etc). There are some more evaluations in there, but I don't think any of them will ever change the result (unused stuff).
But yeah, the maximum possible rlvl for crafts should be 86+12+10 = 108. The alvl of
of Freezing Arrows (on gloves) is 94 btw, so that's only possible to spawn on the Heavy Gloves recipe using a high ilvl rune, and the craft will need to be ilvl 97, so it will have 4 affixes for sure.