It's explained in wrong way.
This "inventory unusable slots" event happens when you use something (drink/eat) without dragging it into your inventory.

To simulate this you should:

1. Find any suitable food/drink (i.e. cola)
2. open your inventory right at this food/drink by "Tab" button
3. eat/drink it without dragging it into your inventory by clicking mouse2 button and choosing "eat/drink"

After that you will successfully eat/drink it, but invisible and empty (0%) jar or banana will take any free slot in your inventory. After relogging or switching server this invisible item will become visible.

I think, if killed guy respawns (by the option in menu) corps disappearing won't happen, but if he leaves the server (and no matter if he does or doesn't re-log in) the corps will disappear. Didn't try either ways but saw how just killed (by me) corpses immediately disappeared.

No fall damage at all, no matter what the height is.

Video confirmation in the last patched version:
http://youtu.be/Cw8kp-T2QRU

minus to the sun problem
plus to the glasses suggestion
:)