It is strange that it doesn't mention unattended objects, but its not that strange.
Fireball says it affects creatures and unattended objects, but most other spells including
Flame Strike and
Scorching Ray just mention creatures. What I was alluding too earlier is that if every spell that didn't mention objects was listed in Stormwrack as not starting fires, it would make sense. But it doesn't work out quite that neatly; the Stormwrack is a lot more random than that, and in any event the list is to check if the spell sets the ship on fire, the spells still deal hit point damage to the areas of the ship within the AoE unless the spell description specifically calls out it doesn't effect objects.
(Personally, I don't particularly care for the Fire Starting list in Stormwrack, because there has to be an easier way than to list a bunch of spells and determining individually if one starts a fire or not. What's wrong with just saying Fire Spells have a chance to start fires? I can remember that. Percentage chance equal to damage taken.)
I still say Opaque means you can't see through it. As in:
dictionary.com said:
1. not transparent or translucent; impenetrable to light; not allowing light to pass through.
I'd say Transparent, No Miss Chance. Translucent, 20% Miss Chance. Opaque, 50% Miss Chance (blind fire). (Though I'll admit that "4. hard to understand; not clear or lucid; obscure:
The problem remains opaque despite explanations." seems applicable as well.)
I'd say absent of something specific in the book, that dealing the spell damage to the objects passing through seems to be as by-the-book as you can make it. I'd deal half damage to objects, but to each his own. Non-magical arrows probably wouldn't make it through (but hey, they're cheap), magical arrows and beefier weapons (spears, daggers, hand axes) probably would, but they'd come out pretty singed.