You have a good point but at the same time if every projects start paying before bounty it still doesn't stop the fact that those coins can be worthless or scam, you can get paid of a token or coin that won't be useful for anyone,
Secondly the moderators on this forum have enough jobs on their hands, that won't be a easy task for those who look after this forum, moderators are humans like us and not super humans
I think it would be great and in fact the mods could also gain some extra money from it,
If they act as an escrow they would surely be paid,
And about the scam or worthless rewards I think it would be great if the escrow would also hold some funds for the bounty participants.
Let's say their promise fund is $100K for the bounty then the escrow would hold 50% before the bounty even starts and the participants could choose to be paid with any crypto that they like.