Pawn doesn't affect inventory item tooltips?
 

EDIT: What addon compliments Pawn in displaying both the inventory item hovered over and the currently-equipped item it is compared against, with Pawn-augmented upgrade info?

I think I used to use EquipCompare or MoncaiCompare but that was years ago.

If I remember correctly, Pawn has that option built into it's settings. I want to say it's on the last tab of options. I'll look in a bit to be sure.

*edit*
I don't see it in the options, but holding LShift while mousing over an item shows the tooltip for currently equipped in addition to the item i'm mousing over.

Comparison tooltips are a feature of the default UI. Hold Shift while mousing over an item to see them. If you don't see them while holding Shift, either you have an addon disabling them (get rid of it or turn that option off), or an addon has messed up your bindings (reset them).