When that happens, what do you do? You cannot submit to another publication. If you pull, it remains self-published.
Is it good etiquette to unpublish your work if it is not the fault of the publication? Not good etiquette - some publications will remove you if you do this repeatedly.
What about when the editor changes your work beyond minor grammatical edits? This is very annoying. I would go in and change it so that it *did* make sense.
Is it good form to tell them first? Usually they won't read private notes once a piece is published. Just go in and fix it.
Hope that helps!