I'd be up for using a template to standardize these notes, similar to an Editor's note in a comic book. For example, if the template used was:
{{EdNote|Things always happen this way, except when they don't.}}
it would be translated as:
(Things always happen this way, except when they don't. - Ed.)
This could eliminate having to use the word "Note," too. Having it be in a certain color would be good, too, though I don't have any specific favorites for it. I'd guess red would be the most appropriate.