Im not trying to wine here or look for a scape goat for my loss but all bias aside I think this is still insane. It defies all utility this service has over low liquidity exchanges. With unpredictable spikes like this you cant trade on margin not long nor short. Im just sad I have to leave the site because I liked it but this is an impossible situation.
I know, it is shit to loose money like this. You would expect all the folks that are using Bitfinix to understand how to use limit orders instead of a market buy like this. But it is not like there are spikes like this every day. And the traders at Bitfinex always seem to be super bullish.
This is not sure to have been a manually entered market buy. It could have been a triggered stop or a margin call (on a previous short). Or a cascade of margin calls/triggered stops, that shot the price up to 400.