I have attached a document that shows the issue.
1. Open the document using Word 2010
2. Enter some text into the text box (linked to flow from lh to rh)
2. Check if Styles are available from ribbon or 'grayed out'
3. If 'grayed out' click where indicated.
4. Styles are now available from ribbon
I have found a work around by inserting the legacy control on the first line - the cursor defaults to that position. However, it is a work around and doesn't explain the behaviour and I prefer positive action rather than relying on default and of course someone could enter a character which would print out.