You're totally right of course! Zombie was last minute so no surprise there's some bugs with his dialogue. The inventory menu normally allows for selling but due to the late addition of the zombie in the jam there was some UI bugs, and there actually is a way to check item effects on the trading floor, just press the I key which will open up the inventory menu and hover over an item. This will bring up a description you can read in the menu. 2.0 for the postjam version is in the planning phase now with a lot more tricks and even consumables, but for now I'll get some bug fixes out after judging has concluded for those minor more annoying bugs