I was trying to confirm the "cold storage spending" feature and change return process with a simple test. It did not work as I expected it to. Hopefully someone can tell me what I did wrong.
I had an address with only 0.25 mBTC in it. I used the Mycelium Cold Storage feature to spend from it. I scanned the private key and had it spend 0.14999 mBTC to one of my Mycelium addresses, and a miner's fee of 0.1 mBTC. I was expecting to see the remaining 0.00000001 mBTC returned as change to the same cold storage address.
Instead, what happened was that the 0.14999 mBTC went to my Mycelium address, but the miner got 0.00010001 mBTC. So, was that new amount an adjusted miner's fee? Or was the miner's fee still 0.1 mBTC, but the change of 0.00000001 mBTC go to the miner?
Reply from Daniel, one of our devs:
I just checked the code - we are combining unpent outputs until we have enough, and if the resulting change is smaller than the dust limit (i.e. would be unspendable), we include it into the miner fee and dont sent it back as change
So yeah, the reason you didn't get change back to the paper was because it would have gotten stuck on there permanently, due to being below the dust threshold. Sorry you had to lose $0.00000347 in that experiment.