Dunno, why is it important?
As far as I know, without checking, anything that can open docx can certainly open doc and rtf files which Libre and oo can certainly save as.
I have an old version of LibreOffice (3.5.1.2) installed though I don't normally use it as I have Office 2007. I just tried saving a .docx file from Writer and it went OK and opened OK in Word.
Libre Office has improved .docx compatibility, but personally I've never really used the format. My daughter tells me she has done homework fine with it though.
OpenOffice.org refused to add support for .docx when it was maintained by Sun and then Oracle.
The .docx patches were maintained separately (but included in the versions of OpenOffice.org that pretty much every Linux distro shipped) and were one of the first things merged when LibreOffice forked, so LibreOffice had support right from the start.
It's possible that OpenOffice.org has added support for .docx now that it's maintained by Apache but LibreOffice is so far ahead of OpenOffice.org now that there's really no reason to use OOo over LO.
Comments
As far as I know, without checking, anything that can open docx can certainly open doc and rtf files which Libre and oo can certainly save as.
The .docx patches were maintained separately (but included in the versions of OpenOffice.org that pretty much every Linux distro shipped) and were one of the first things merged when LibreOffice forked, so LibreOffice had support right from the start.
It's possible that OpenOffice.org has added support for .docx now that it's maintained by Apache but LibreOffice is so far ahead of OpenOffice.org now that there's really no reason to use OOo over LO.