LibreOffice versions: 5.1, 22.214.171.124
OS: Elementary OS 0.4.1 x64 (a derivation of Ubuntu 16.04.2)
When I protect a sheet, the all comments I wrote on cells will be removed.
The steps to re-experience the issue:
- open a blank sheet
- right clik on any cell and select the command of “insert comment”
- write down some text
- right clik on the current sheet name from the bottom of the sheet
- select the command of “protect sheet”
- press on “OK” button on the dialog window (so, give a blank password)
- save the current file with “*.xlsx” (MS Excel 2007-2019) file extension and close Calc application
- re-open the file
Now it can be seen that there is no any comment on any cell, unfortunately…
Mike Kaganski has pointed out to file format. My file extension was xlsx. I’hve corrected the steps above.