So that gives you the right to take out a 100 btc credit line with me, use over 10 BTC of it, and never repay it?

I don't care how honest you are in your other dealings, I'd expect you to be. In this dealing you have given IOUs which were NOT worthless to other users, then taken a BTC debt out with me and passed it on. When you gave that 15 BTC IOU after everything had been proved, you knew exactly what would happen, or indeed arranged it.

Argue about terms, times, whatever, you have an outstanding credit line of 10.15 BTC with me, 9.15 BTC which I demand back. When will you be paying this?

Blockchain 1BqZohTvZ6KmPFj9ThS3CeGqpm3hJYfSqo or Ripple are both fine. You know my ripple address, I've reduced my trust to you so you can't incur any more debt, since you've proved very untrustworthy in the past 24 hours, certainly when dealing with me through ripple. I cannot speak to your other services or transactions, nor do I care about them.

I obviously do see the conflict of interests between code that allows people to lend to their friends and a business which makes money from lending coins though, but perhaps you are just ripping me off to prevent other people from getting ripped off (!?). You/we demonstrated (a) how a system works, (b) that you were untrustworthy.

In this demonstration you played the part of the scammer, the untrustworthy gateway, and I played the part of the hapless victim (to prevent some newb from loosing up to 100 btc). Only after everything was proved, you took it one step further and really did take 9.15 BTC from me.