Office button, Word Options, Advanced tab, Editing options, remove the check
next to Keep track of formatting. This takes care of the showing direct
formatting as styles.
To limit just to styles in use, press Ctrl+Alt+Shift+S, click Options (at
the bottom of the Styles pane), and set Selected styles to show to In Use.
Note the option at the bottom to set this only for the current document
versus for new documents based on the current template.