I know what you mean. I will try to find it now, but it can take a while..
Try this one:
http://img410.imageshack.us/my.php?i...5059295as6.jpg
This button switching design/text mode. If the "design mode" is enabled, you can copy your materials WITH oryginal formating.
If you switch this to the "text mode" you cant do it. In text mode, you allso see a bb code tags in your message.
However, i cant find the place in ACP where you can make this settings default for all users. Maybe its impossible

Probably you will need to inform your redactors about this button manualy