Items in BatMUD have many, many variables. Some are visible to mortals, some
are not. Stacks that do not join with each other fail to do so because they
are different in some significant way. Sometimes the player might agree
they're important reasons (one is enchanted, the other is not) and sometimes
they wouldn't (one is identified, the other is not). Making a save container
that works only by number of arrows would be like making a chest that works by
total sac value, allowing the storage of several thousand herbs. This is
simply not how data of chested items is saved, and putting one in an already
crowded chest room would quickly lead to a bugged and _empty_ chest room.

Player-made arrows are made with almost no random stats whatsoever. As such,
one player using the same materials should be able to make arrows indefinitely
and they will all stack. Player-made arrows are also expected to be the major
supply for archer shots. Monster-generated arrow bundles are small and have
too many random features and, as such, won't stack with anything else. Your
best bet is to either save a large bundle or random good arrows for an eq
monster fight, or burn them off quickly so you don't have to waste a chest
slot on them.

The idea has come up before where an "arrow converter" would let you merge
several non-matching bundles together. If such a thing did exist, it would
have to make the result not only generic, but the lowest common denominator --
i.e. the lowest quality, most damaged, etc. You don't want that to happen.

P.S. Coffers are special because money only has 2 variables, "what metal" and
"how many".

Shinarae Lluminus