Christian Moe <mail@christianmoe.com> writes:

> I don't think it's specific to ODT or LibreOffice, it's the underlying
> XML 1.0 spec that "discourages" control characters and does not include
> #xC in the range of characters that XML processors must accept.
>
> Spec: https://www.w3.org/TR/REC-xml/#charsets
>
> Some discussion:
> https://stackoverflow.com/questions/404107/why-are-control-characters-illegal-in-xml-1-0

Thanks!
Then, we can simply remove the disallowed characters.
See the attached tentative patch.