Found a workaround.
Change the shortcut to something custom in Xcode
Open ~/Library/Developer/Xcode/UserData/Keybindings/Default.idekeybindings in a text editor
Change the shortcut to @$7
i.e.
<key>Keyboard Shortcut</key>
<string>@$7</string>
You'll need to do it for all 4 comment shortcuts.
Topic:
Developer Tools & Services
SubTopic:
Xcode
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