If you are currently holding an item in your hand and left-click on a square containing another item you will move to collect it, destroying the item you originally had. I didn't see it on the first 7 or so pages but it's probably quite a minor thing so long as you use WASD to walk around while holding items.
I can't reproduce this? when I click on a square with other items, the item I'm currently holding drops to the ground.
In order to reproduce the bug you need an item on the ground, say any more than two spaces away. Hold an item in your hand and click on the item on the ground, the key is that you have to walk some distance to get to the item.
Okay, I got it working (it only works in certain item types.) Thanks for the report, we'll look into it.
No problem, if I find other bugs should a separate topic be made for each, or would merging them be more appropriate?
Go ahead and post a new thread if you don't see it in the known issues list or in the last couple pages.