I ended up shorting some to myself at price feed
I understand this will leave you with both a short and a long which in effect cancel each other out. So you may just be wasting fees and exposing yourself to margin call risks. Is there any reason why anybody would want to create shorts to buy themselves?
You are correct, but I can think of a few reasons why buying your own short makes sense.
One reason one might want to do that is because they want to rollover their existing short. They can use the BitAssets collected from matching their own new short to cover previous shorts. That could potentially be a smarter move to do when the market is inactive and there are no BitAsset sells at or below the price feed, then waiting until the 30 days expire and having the blockchain do it for you, potentially matching against someone else's short that gets in front of you in the order book. It also makes a lot of sense to intentionally roll over before the 30 days if you can rollover at a profit and the top interest rate offered by shorts in the order book is less than the interest rate you are currently paying on your shorts.
Also, even if you have no existing shorts, it could make sense to buy your own short if you intend to gradually increase your exposure to BTS. So you plan on going short on the BitAsset, but you want to do it gradually. But if there is a great opportunity to short while the interest rate is zero, you can take advantage of that by shorting to yourself. Then over time you would slowly sell your BitAssets for more BTS (or even spend your BitAssets for goods/services).
Finally, the most likely reason why mdj bought his own short is because he wanted to get in on early CFSGold
ownership while he still could. While that doesn't change his overall exposure to BTS and gold (assuming he can trust CFSGold to at least maintain the value of BitGold), it does allow him to be a sharedrop target for 10% of CFS.