I hope we can close this issue now, as updates should be included in TeX Live.

Thank you. I have confirmed that sample.odt produced
the desired .docx output.

I provide a more complex example. Could you confirm
that the latest make4ht gives the correct result?

%%%
\documentclass[12pt,a4paper]{article}

\usepackage[comma,colon]{natbib}

\usepackage[OT2,T1]{fontenc}
\usepackage[english,russian]{babel}

\begin{document}

\selectlanguage{english}

\textit{test italic} \& {\it test italic}

\begin{thebibliography}{}

\bibitem[{Bragin}(2003)]{bra03kustanai}
{Bragin}, E.~A. (2003) \selectlanguage{russian}
{Ornitologi{ch}eskie issledovani{ya} v Kustana{i0}sko{i0} oblasti
v 2003 godu }\selectlanguage{english}{{Ornithological} research in
{Kustanai} region in 2003}. {\it Kazakhstan Ornithol. Bull.\,} 2: 41-46 (in
Russian.)

\bibitem[{Ryabitsev}(2008)]{rya08uralbirds}
{Ryabitsev}, V.~K. (2008) \textit{\selectlanguage{russian}
{Pti{ts}y Urala, Priural{p1}{ya} i Zapadno{i0} Sibiri }
\selectlanguage{english}{The birds of the Urals, Ural Upland and Western
Siberia}.} Yekaterinburg: Ural Univ. Publishing House
(in Russian.)

\bibitem[{Alekseenko}(2016)]{ale16baikalraptorphd}
{Alekseenko}, M.~N. (2016) \textit{Ecological aspects of fall migration of
raptors in south Baikal migration corridor.} PhD Thesis, Bratsk State Univ.,
Bratsk (in Russian.)

\bibitem[{Antonov}(2020)]{ant20middleamur}
{Antonov}, A.~I. (2020) Expansion of new bird species in the {Middle Amur}
region at the end of the 20th century: the role of climatic changes. {\it
Rus. J. Ornithol.} 29: 4819-4827 (in Russian.)

\end{thebibliography}

\end{document}

The following source gives different results for \textit
and \it in .odt. After conversion from .odt to .docx,
all italics in the reference part are converted to roman.

%%%
\documentclass[12pt,a4paper]{article}

\usepackage[comma,colon]{natbib}

\usepackage[OT2,T1]{fontenc}
\usepackage[english,russian]{babel}

\begin{document}

\selectlanguage{english}

\textit{test italic} \& {\it test italic}

\begin{thebibliography}{}

\bibitem[{Alekseenko}(2016)]{ale16baikalraptorphd}
{Alekseenko}, M.~N. (2016) \textit{Ecological aspects of fall migration of
raptors in south Baikal migration corridor.} PhD Thesis, Bratsk State Univ.,
Bratsk (in Russian.)

\bibitem[{Antonov}(2020)]{ant20middleamur}
{Antonov}, A.~I. (2020) Expansion of new bird species in the {Middle Amur}
region at the end of the 20th century: the role of climatic changes. {\it
Rus. J. Ornithol.} 29: 4819-4827 (in Russian.)

\end{thebibliography}

\end{document}