I suppose it would be very much like downtime you'd see if you were upgrading any large CMS.
Have you tried using nginx to automatically send users to a pre-determined, statically-hosted error page if the connection to NodeBB 502s?
I participate in the http://mangolassi.it community and just noticed that if you hover over the "replied about 18 hours ago" text, you see the actual timestamp. Great little gem. Can it be set to show something more readable though?
Just found this thread and wanted to say thanks for updating the hover text.