This is a feature tweak suggestion.
Currently if you share a note with someone using the Share on Web feature and then later move the note to trash the other users are still able to access the content of the note. To me this doesn’t seem natural as the intention of moving a note to trash is in a sense to make it irrelevant/inaccessible, and you might forget about having shared the note.
I therefor suggest that the sharing on a note is automatically disabled when moving a note to trash, and then maybe automatically turned on again if the note is restored from trash. But I’m not really sure if the automatic re-enabling part is a good idea.