Technically, it should be no harder than the "delete" button, which has been the de facto "edit" button up until now. The article itself talks about how defini

Technically, it should be no harder than the "delete" button, which has been the de facto "edit" button up until now. The article itself talks about how defining the feature from a product perspective was really the hard part, and I'd say it makes sense to take that at face value. You really do want to be able to see when a text has been edited, there do need to be some limits, etc. and defining those things is not trivial by any means.