I really don't know why you bother. Give them the template and train them to
use it.

Hi Lisa

I think the best approach is to create character styles called Bold and
Italic and Underline and whatever (or, use the built-in Strong and Emphasis
styles). And in your template re-map the ordinary Bold and Italic buttons so
they apply your chosen style (to do that, use Tools > Customize etc, create
a button to apply each of your styles, copy the images from the existing
buttons to the new ones, and then delete the old buttons).

You'll need to re-map ctrl-b, ctrl-i, ctrl-u etc, too.

Make sure that your customizations are saved in the template, not in your
normal.dot.

This gives users a consistent interface, but you can retain the protection
for styles.

You might also think about what paragraph settings you want to make
available to users. For example, it bothers me that if I protect a document
for styles, a user can't set a paragraph with "keep with next" or "page
break before". That encourages the really awful habit of inserting manual
page breaks which seriously lowers user productivity as well as having
unfortunate side effects.

Hope this helps.

Shauna Kelly.  Microsoft MVP.
http://www.shaunakelly.com/word