He sold 100 at 0.04 (and received 4 HIVE for that transaction) but he also sold 650 at 0.00000001, and received 0.00006 HIVE for that transaction.
By 'liquidity' I am referring to the small number of tokens available to buy or sell. If just one person decides to sell and there is no BUY wall (as was the case when @scholaris.pob decided to sell) then the price will go to zero, if that person is willing to sell at whatever price he/she can get.
I noticed as well another thing. I had there a sell order for 1 hive each. It was 10k when I put it there and it turned to about 9700 or something like that. It was canceled automatically. I don't know if they have limits for orders to stay there, or what exactly happened there. Maybe a bug or something, but that order was there for almost a month or more. So, I've seen others putting orders for 0.8 and 0.9 and they are still there. I told myself, let them sell to enjoy that money. That's why I didn't ask developers about the situation. I don't know if you know something about that or no. Could they cancel orders automatically ?
I believe Hive-Engine puts time limits on BUY and SELL orders (i.e. they automatically expire after a certain amount of time -- I'm not sure how long that is, a couple weeks, I think).