Since auction house fees are one way to sink IGC out of the economy, it stands to reason that giving people more reasons to buy and sell items would tend to be a counter-inflationary measure.

So anything that's good for commerce, in general, that is anything that spurs people on to buy/sell items, is a good thing.

For this reason, I think things like "Use merits to circumvent the auction house and generate items ex nihilo" scare me a little, but I think if you make the amount of merits fairly high AND you add in a fairly high IGC cost to get/craft the item, it's not the end of the world.

Obviously, if every item that dropped in the game had a limited lifetime in the game, period, that would do it too. Like no repairing, no gear degradation, just "it lasts for X number of uses of for some finite time period, then disappears forever and you have to go get a new one". Magic: The Gathering works like that, they keep rotating different sets into and out of the Standard tournament format such that you can't just make one deck and play it forever. That way they keep selling cards to people. Chances are people would hate that, though, and you'd have to make the lifetime of the items so long that it may as well be infinite. Magic cards stay in Standard for like 1-2 years after they've been released.

Another idea is that giving people reasons to unslot/reslot their items in their builds over time is a good thing. What complicates that is the fact that the buyer and seller both need to have reasons to buy and sell those items. So you end up wanting to find a way to make a given item more desirable for one person than for another over time in some sort of long-term cyclic way, like wearing heavy, warm clothes in the winter and lighter ones in the summer. I suppose you could just give each Augment and Refinement a sort of waxing/waning "lunar cycle" that modulates it's effectiveness over long periods of time, such that you might want to sell your Damage Augment soon so as to replace it with one that will be more effective for the next few months, etc. That would cause the less effective ones to be cheaper and the more effective ones to be more expensive and people COULD try to arbitrage that by stocking up on cheaper stuff and then selling it when it get's good again later. Augments and Refinements would be more, "seasonal" in that sense maybe. But that arbitrage would require more storage space for more items, one assumes, and people might be paying IGC or Stars for that space, which means selling more of that to more people, maybe, which could be good too.

How to create/promote MORE commerce, that is the question...