I reviewed a scientific manuscript of a colleague an wrote comments on general text paragraphs and on text in text boxes (figure captions).
When I saved the file in docx-format and re-opened it, all comments on text boxes were gone, but the comments on other text paragraphs were still in place.
When you save the file in docx-format the comments on text boxes are still shown, so you expect that they have been saved.
Steps to Reproduce:
1. Open a docx-file with text boxes generated by MS Word in Libreoffice writer.
2. Write a comment on text in text boxes
3. Save in docx.format.
4. Close and reopen the file.
Comment on text in text box is gone.
Comment should be saved.
User Profile Reset: No
OpenGL enabled: Yes
A file to test the bug can be downloaded here
It doesn't seem to be supported in DOCX format, as Word doesn't allow adding a comment to text inside tezt boxes. I'm inclined to close this as NOTABUG for that reason.
I agree, that there is no need to save comments on text in text boxes if MS Word does not support in the docx-format.
Nevertheless it is a considerable annoyance to the user, if text just disappears after saving and reopening a file.
As far as I can see, you can not comment on text boxes, that were generated in LibreOffice Writer. Thus, comments on text boxes is not a feature in LibreOffice in general.
To avoid frustration about disappearing comments, I would suggest to disable comments on text in text boxes generated in MS Word as well.
*** This bug has been marked as a duplicate of bug 135794 ***