Removing Items from Inventory changes Kerbal's mass before it is "set down"
After doing a "no parachute" re-entry, I decided to jump ship and use the Kerbal's parachute to land.
I messed around with the new inventory, and thought: It would be great to not have this heavy jet pack while I'm in my parachute.
I "picked" up the item out of inventory. Then tried to "drop" it into the air. I couldn't get it to drop so I put it back in inventory.
I noticed that as long as I had the item "picked up" and not on the inventory slot, the weight of the item did not count to the Kerbal's mass.
I know the screen shots I got don't quite show the mass change (except the associated fuel) but I was also able to change my speed in the parachute by doing the same thing as the images show.
Note the mass is lower. The fuel is lower
Note it's back, but I still haven't dropped it into inventory.
The mass should not change until the inventory item is on the ground. (or dropped if it can be)