I have long speculated that he has figured out the formula that theymos uses to calculate how much each moderator gets from the forum ad sales, and that grue pads his moderator activity to increase his payout. If you exclude the amount that BadBear gets, then grue makes well over 2x the amount that the next highest paid moderator gets on a consistent basis. The problem is that this is very difficult to prove as most of the information needed to prove this is unavailable to me.
It's unavailable to everyone but theymos but there's probably not much to figure out - handle a lot of reports / move threads and get paid for them. Theymos has stated before that deleting posts doesn't account for much (which is probably a good idea) and I delete a hell of a lot of bumps in the marketplace and don't get paid any more for them so that's likely not an issue. I think the mod money that is allocated is capped to certain staff levels. Patrollers seem to get a max of around 2btc or so if they're very active whereas very active Globals like grue and BadBear get near or around 8btc (though I believe it's dished out by the dollar value so it will fluctuate from time to time but the payments in comparison are roughly the same). I've always got the same even when when I got promoted from Patroller to both mod of the entire Marketplace and Bitcoin Discussion. I must be handling at least double of what I was yet I still get the same and the same as when I was just a patroller and the same as other very active patrollers or mods of a local board so I reckon it's just capped by staff position. It would be interesting to see who handles the most reports / makes the most mod actions but maybe then people could game the system but there doesn't seem much that active mods could do to get more if they're already hitting their staff level thresholds etc.
The total payment to all of the moderators is 25% of the forum ad sales, so if the ads sell for a higher amount then the mods as a whole will get more.
The exact formula is secret, although if you keep track of what actions you take and how much you are paid then you should be able to figure out what actions are worth the most and taking those kinds of actions even when they might not be necessary. For example sending a PM to someone in relation to a moderation (e.g. being from a moderator as a moderator) likely causes that moderator action to be "worth" more or is separately worth something in itself. One of my alts once had
one of it's posts deleted when I replied to a post of Bruno about something that grue claimed was off topic, this was far from a trend and was probably unnecessary to receive a PM about it, however I got a PM around the time the post was deleted saying that my post was deleted because it was a reply to an off topic post.
I would think that the payment is not based on responsibilities, but rather by actions taken. It is just that a higher ranking staff member would have more opportunities to take additional actions, and potentially more valuable actions.