Is it possible in vim to understand why a particular word stands out as it is? In particular, I have set spellon, and in some situations it got a weird highlight. Obviously, this is not limited to spell checking.
set spell
I have something like this in my status bar:
:echo synIDattr(synID(line("."), col("."), 1), "name")
Shows how vim parsed the syntax of the element under the cursor, which you can use to find out the source of the selection.