diff --git a/README.md b/README.md
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@@ -199,6 +199,12 @@ Some Stack Overflow discussions:
 
 We commit to describing the exact interactions between the two proposals on the path to stage 2/3. See [issue #3](https://github.com/tc39/proposal-regexp-set-notation/issues/3) for details.
 
+### What about symmetric difference?
+
+We considered also proposing an operator for symmetric difference (see [issue #5](https://github.com/tc39/proposal-regexp-set-notation/issues/5)), but we did not find a good use case and wanted to keep the proposal simple.
+
+Instead, we are proposing to reserve doubled ASCII punctuation and symbols for future use. That will allow for future proposals to add `~~` for example, as suggested in [UTS \#18](https://www.unicode.org/reports/tr18/#Subtraction_and_Intersection), for symmetric difference.
+
 ## TC39 meeting notes
 
 - [November 2020](https://github.com/tc39/notes/blob/master/meetings/2020-11/nov-18.md#adopting-unicode-behavior-for-set-notation-in-regular-expressions)