Say a quest is not repeatable it could happen that for some reason a quest item goes missing from inventory. A plausable example (where no fault is involved although there may be others where it is) would be if a person is subject to a weakness spell, the inventory gets dropped and picked up by another. Assume the quest item has no eceonomic value in this case.
At this point the quest is irrevocably lost since it cannot be restarted (discarded).
If non-discardability is a given then possibly allowing reinstatement of a quest item where the quest has been given, the item obtained but lost, might smooth things over.

Rational:
If you are not a skilled appraiser of weapons or a skilled swordsman it stands to reason that you would not really know a silverweave /10 from a fancy /0
In the same way that you need some intellignce to know accurately if you are stronger or weaker than someone else the same could apply to weapons.
If you loot a sword from a corpse it does not come with a training manual after all.

Assume for a moment you do the following:
Removing the damage stats of a weapon from player view. From a RP point of view how would you know??
Introducing good looking but inferior weapons (like fake silverweaves)
Removing the combat damage numbers. (system tab). If you want rather have something like: tickle hit lightly, bludgeon, oblitterate and so forth if you have towrite anything informative.

The Result
You wont know if a sword is any good unless you have tried it or you have some kind of skill that tells you.
Also with good looking but useless weapons out there it will bring trading prices down to a more reasonable level.
If you cannot accurately appraise a sword then you may just be selling a /10 for a pittance and not know.