1 charm = same
2 charms = trade
3 charms = random item
As to that question, I believe he was talking about having the option to use more than one charm on a single roll. So if you use one, it works the same as now. If you elect to use 2 charms, then you can trade a drop you have for a different one on that loot table. Like if you have the helm and you just got another helm, you could choose to use 2 charms and trade that for the sha-touched weapon. And finally for using all 3 charms on one roll, you are guaranteed a drop but it's random from the loot table.
"he doens't need healing, he doesn't need healing, he doesn't nee-WHAOSHIT!wtf was that man!". Please stop leaning on TDR. -Teng