As of latest experimental 6847e86.
In the inventory screen, a character’s total volume is shown at -2 from what it should be. So a naked character will be shown to have 0/-2 available volume.
Example:
I suspect this is just a display bug confined to the inventory screen. It doesn’t seem to appear in any other places where available volume is shown, such as the “pick up” UI or the advanced inventory, and it doesn’t seem to affect the character’s ability to pick things up.