What part doesn't work?
I presume you mean the previous item display bug?
Are you using chrome?
And of course did you remember to disable the other version of the script?
I only tested this in firefox so far.
You are right... testing on chrome, it does nothing. Behaves like no script.
Well, found some interesting differences between Chrome and Firefox behavior.
For both original and my version, Chrome is calling additionalContent.itemInfo() before the script replaces it, so the original stock WK version is getting registered on the click handler. On your version at the end you call additionalContent.itemInfo() at the end of the script. That makes it work in chrome since otherwise the replacement function would never be called, but it also means that both the original function and the replacement function have registered different click handlers and both are getting called. Adding the additionalContent.itemInfo() to the end of my version gets it sort of working, but then a $("#additional-content-load").hide() is needed as you had in your version because the other click handler is calling $("#additional-content-load").show().
My version also experiences the sending extra requests on hiding bug with these changes. And in chrome the space bar don't re-hide fix is broken by the original function running.
Firefox does NOT call additionalContent.itemInfo() before the userscript replaces it, so there is only the replacement version running.
So that is why I did not encounter these problems before.
Try it again on Chrome. I think it is fixed now.
Deleted all click handlers for the "#option-item-info" button.
This gets rid of the stock WK click handler that was causing problems.
Replaced two other necessary handlers that were deleted.