Offline issue
Heads up: some users have reported that Reviewable has started going offline all the time, causing them to lose work. I'm still investigating but so far it appears to be restricted to the recently released Chrome v72.
If this happens to you, know that you can run Reviewable.workOfflineAtMyOwnRisk() from the console to get rid of the modal dialog and copy out any recent edits. It also appears that using incognito mode works around the issue, as does wiping local storage and Indexed DB for reviewable.io and refreshing the page.
The situation is developing and I'll make sure to post any updates here. If you're affected and want to help debug, please drop by the chat room. Thanks!