Level 31 & Level 30 characters can authorize the use of those funds for "Clan Purposes" (avatar, etc.) - but no one can withdrawal.
What is a clan purpose?
"We need a clan dwellings" ..hm, maybe --> then the leader sells it, gets the gems...well, you know the trick
"We need an avatar" ..hm, maybe
"We are at war, our leader needs gems to do xyz" <--hmmm
I don't want these discussions to come up. Once you HAVE such coffers, believe me, it will be you who answers petitions who have these things in them
It's a thing I still have with the coffers "why can't we deposit gems!" that regularly comes up.
It's not a good thing. Really. Gemstorages will always be abused, sooner or later, or at least make me seem like an evil man that gives out stuff but refuses to let people use it like they want...