Sorry, you cannot.
TRichView always saves Unicode characters having codes greater than 127 as RTF Unicode characters.
You can only remove non-Unicode duplicates of characters (\'d3 in you example), exclude rvrtfDuplicateUnicode from RTFOptions properties.
Saving Unicode characters as Unicode characters in RTF is necessary.
If we would save only non-Unicode duplicate (\'d3), it can be read correctly only if its Charset is specified correctly. It is not necessary so in TRichView Unicode documents.
And RTF specification does not allow saving characters having codes greater than 127 as they are.