IMO, offline read-only is enough of a compromise. How many times are users truly offline, AND want to be able to edit at that time (and deal with the potential conflicts, which by the nature of the operation, won't have a good UX)?

In my case quite a lot of the time. Which is why Google Keep as a web app is useless but the Android version is very useful.

Also I don't understand why so many people on HN are concentrating on the simultaneous editing scenario, for most ordinary people this is actually quite a rare event especially in their private lives. Google Keep on Android seems to work pretty well in his context my family uses it to share shopping lists and other notes very successfully even hough several of us are online only intermittently.

Offline read-only would already be a great feature for me, knowing that my data is always close to machine. But, my guess is that this isn't enough of a killer feature for most people to care.

Any time looking at the RO data directly triggers a need to edit it. Eg, you notice a typo or a mistake, you get the idea for a follow up or clarification, etc.