If you are using an editor or system that does not support Unicode you will need to EXPORT your LibO file to downgrade the support character set. For example .txt. This will allow you to select ISO-8859-1 which should be supported by your prowritingaid. If not you could try US-ASCII as the system appears to only understand English. (I think, we in Europe would say English-US, rather than English-GB)
You will probably have the same problem if you COPY/PASTE to go over to Chrome.
What keyboard setting, language setup, data types does prowriting support?
Libreoffice and the Internet default to Unicode, the International standard since 1997 which supports about 138,000 characters.
Unicode includes ISO-8859-1 (1987 vintage) which supports the first 255 characters used in Western Europe including England and France. And it supports US-ASCII (1968 vintage) the first 127 characters used in America.
As I mentioned above, if you copy and paste the system must support Unicode. If not you will have this problem. Also, if you EXPORT to a RTF file you must specify the character set your system understands. Otherwise the file again will be still Unicode. Have you defined your Chrome system Keyboard to support Unicode (UTF-8)?
It is importance to understand that copy / paste from one file to another, even if both are Libreoffice .odt files is controlled by the operating system settings, including language. The fact that both files use Unicode (UTF-8) is overuled by your operating system. A bit like having a colour camera, television but black and white film. I assume that one of your problems is there. Language is also important. If you are in Europe and use the € (Euro) sign, for example, you would have the same type of problem. This is why I asked what keyboard and Language settings you have defined. You may have not set these things yourself but they are important to sort out your problem which must be frustrating for you.
By the way, most of my users are not programmers.
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Updated to consider Apostophie and Quotation Mark situation
One problem that can add slightly to this conversion problem and shows why it is important to know the operating system language, LibreOffice language setting and language used for cutting and pasting. Or to put it another way, what you think you are typing is not actually what you get.
I quote from the Unicode Manual.
“Most keyboard layouts support only the U+0022 ( " ) QUOTATION MARK therefore word processors commonly offer a facility for automatically converting the U+0022 ( " ) QUOTATION MARK to a contextually selected curly quote glyph.”
These conversions are language dependant. So, for example, English and Dutch are not the same a Danish and Finnish or French. Also, the Apostrophe used in publishing is often “improved” by upgrading it to a quotation mark. As the Old US-ASCII and ISO-8859-1 support only the 0022 and 0027 you can see this leads to problems highlighted in this question.
Apostrophe U+0027 ( ’ )
Quotation Mark U+0022 ( " )
Left Single Quotation Mark U+2018 ( ‘ )
Right Single Quotation Mark U+2019 ( ’ )
Left Double Quotation Mark U+201C ( “ )
Right Double Quotation Mark U+201C ( ” )
On the Linux and Windows versions of LibreOffice you can display the character code by using ALT-X.