Hello all,
Yes you can pile up conditions on a creature without a limit. The word duplicate meant "repeatedly stack without limit".
Stacking conditions is very powerful! However, some conditions, when stacked repeatedly, offer little or no additional benefits - such as Stun or Daze. A stack of Weak conditions on an an enemy Mage can take him down to 1 attack dice and then offer no further benefit (until or unless he buffs). Stacking that many on a Mage will take a little effort, but if it can be pulled off it's very satisfying!
A Purify spell can remove all of the Weak, Rot, Cripple, or other poison conditions and enchantments on a creature, all at once. Geyser can remove all of the Burns. Future spells will continue to offer opportunities to remove condition markers, such as the coming Wand of Healing, Renewing Spring, and Clear Mind spell.
Hope this helps!