I think the issue is some people never pressed f10. I am not sure why. The keyboard command sheet included with the game illustrates this is possible. (image taken from an ebay listing)
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The game booklet also has the same keyboard commands on pages 73-74. I recently rediscovered my game booklet, and it also has screenshots of the transparent UI. They are in black and white unfortunately.
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Here is a player doing the butcherblock hammer quest.
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If you pressed your Persona key, you would see stone borders, without inventory open.
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If you pressed your inventory key, or opened persona and clicked Inventory button, you would see this:
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For good measure, here is one my first screenshots.
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Hope this helps someone!