BTW, just remembered a weird one, concerning "styles in use":

-- Create a table.
-- Assign some style, say "Test1" to one cell (say by typing that name in
the style dropdown).
-- Assign another style "Test2" to the cell below.
-- Merge the two cells.

-- The merged cell is in style "Test2", and nothing in the document is in
style "Test1".

The styles and formatting pane, though, will show you that "Test1" is still
used once, but won't select anything if you "Select all instances".

Now split the cell again (one column, two rows): The upper cell will
magically be formatted in "Test1" again.

You could say that a feature (Word remembering the styles of merged cells)
results in a bug (Word reporting styles "in use" that aren't actually --
visibly -- used).

:-/ Klaus