What counts as 'in the hands of'?
A weapon's quality is determined by the person who wields it. A city gate's is determined by the overall faith of the city's inhabitants.
If 1% of the inhabitants were not worshippers, 42% were worshippers, 18% were primary worshippers, and 39% were exclusive worshippers, the gates would have the quality of copper. The gates would not get super strong if an exclusive worshipper touched them, save if that worshipper ripped off the gates and started beating people with them.
What happens if an exclusive worshiper and a non-worshiper (or any combination) grab an object made of the metal at the same time?
I'd think it takes the properties of the most powerful one (the exclusive worshipper).
If it didn't, then it couldn't harm non-believers, as the blade would turn to tin when it struck.
This...well, kinda. If it didn't, the metal would turn
as bad as tin but it won't turn into actual tin.
What happens if one makes an alloy with it, which then changes hands?
It gets better or worse depending on who holds it.
Edit: Also, won't it make non-worshiper smiths popular among worshipers, as the metal is easy to cast and very malleable to them?
It's a magic metal that gets "better" or "worse" depending on who's using it. The tin/copper/steel/katanite comparison is just an aid. Devout smiths can work it more easily, swords made with it get sharper and lighter, alloys with the metal infused do what the alloy is supposed to do better, etcetera.
Of you have any more questions, don't hesitate to ask. The more detailed the description becomes, the more likely it'll do what I expect it to do.
Like for example, a blessing that makes someone's exerted strength increase without altering biology would make sense for it being disabled. However a blessing that alters a persons biology to superdense musclemass would not make sense for disablement. Cause it's no longer a divine force at that point.
Actually, there is. A divine force is present and being used to alter the person's biology.