An update in case it helps others.... the 'official' response from QB is that natively this isnt supported as only single-byte characters are currently supported BUT that it is something QB is working on to support in the near future.
In the meantime I did discover a workaround that seems to work for my needs- although may still be dependent on customer's browser settings.
In my external service that is managing these strings and making the QB API calls I did two things:
1. First I HTML encoded the strings
2. Then, I base64 encoded the strings
I sent the base64 encoded string through as part of the XML payload of the addrecord API call. On the QB side I created a formula- rich text field which decodes the base64 string... the result is an HTML encoded string that displays correctly in the rich text field
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Scott Pugh
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