In DTP 2.9.11, I find that converting a formatted note to an RTF note results in a duplicate: an RTF note in addition to the original formatted note. Is that by design?
Yes, the original is left intact.
So that if you don’t like the results of the conversion, you’re not stuck without the original document. In OS X, most apps that do conversions also do it non-destructively.
I have been grateful for this behaviour more times than I can count.