A tentative hint!
Custom components can be used to store notes… I haven’t run any such model yet but there are no errors indicated and it is a useful (to me) way of keeping info in the model without embedding comments in the code of the components, which would then make them customised and their settings inaccessible via the settings panel
Admittedly I do get this “error” relating to previews when I save one of my comment components, but everything seems fine otherwise.