Why are headers and footers jammed?

If height of a header content exceeds the header's region height, the header is clipped in its region and some bottom lines disappear (the overflow trait controls this). Footers behave in the same manner. We set the overflow trait for headers and footers to be "visible", but some rendering tools ignore this trait and clip these regions. From the other side, if this trait is processed, a body text just below the header or above the footer could be overlapped with the header or footer text and it could disappear also. So, to provide the full visibility of headers, footers, and body text, increase top and/or bottom margins of the RTF document.