I wish to inform that LibreOffice have received a modification, to address the problem of emspace in odt.

Here is the information:

Regina Henschel 2016-12-02 16:14:37 UTC

The commit https://cgit.freedesktop.org/libreoffice/core/commit/?id=074f0ab1d76f16fe92493868e2f2de75e67792ef 
has fixed the import of mspace as ~ and `. The .odt file looks good for me.

Viewing the formula in the docx-file is a different problem. 
The formula in the docx file uses the character U+2001 to generate the space.