In Word 2010, when I set up a flow chart and insert a shape, and click in the shape, a cursor appears, but when I enter text no text appears.
If the text is spelled wrong, a curly red underline appears to indicate misspelling. Thus it is apparent that the program recognizes that text is being entered.
Clicking on "no fill" does not cause the text to be displayed. Nor does altering the alignment of the text.
OF COURSE, inserting a text box will provisionally solve the problem. However, the purpose of the present question is to determine whether inserting a text box is necessary.