Can RTC compare *.docx file using word compare?

 On Eclipse 3.6, you can add the .docx content type manually to the Word Document type that Geoff indicated above (i.e. duplicate the way Eclipse 4.2 is configured out of the box).

 We use Eclipse 3.6 and face the same problem when diff'ing docx files. Hex dump is presented in Eclipse. We use instead the RTC 4.0.7 Windows Explorer Shell Integration and configure BeyondCompare to handle the diff. Beyond Compare extracts text from word documents and presents a diff window in for the text.

Hi Jia,
It seems to be available since Eclipse 3.7 and 4.2: This is Eclipse defect implementing this: https://bugs.eclipse.org/bugs/show_bug.cgi?id=343241

Let us know if it helps you.

When you say "RTC compare", which RTC client are you referring to?
If you are referring to the Eclipse client, this is actually an Eclipse question, rather than an RTC question (RTC by default invokes whatever is declared for the Eclipse compare machinery).
To see what file types will invoke the Eclipse word compare machinery, go to your General->Content_Types preference page, and see what file types are under "Word Document".   In my Eclipse 4.2 client, I see both "*.doc" and "*.docx", and files of either type compare properly for me (i.e. use the Word compare machinery) when I invoke the RTC "compare" operation on two different versions.

I am not aware of any automation that would do this. As far as I can tell these files are treated with binaries. You should lock the file on the stream if you want to edit it. That is the model my team uses.
If you find an external compare tool that you can use with RTC you might have a chance.