Apollo had this same bug before the API-colypse, and it’s supposedly because iOS memory management doesn’t actually alert an app that it’s being closed in the background. When you swipe away from an app, the phone automatically determines when to close it in the background; Even if it is still visible on your list of running apps, it may actually be closed. (This is also why iOS doesn’t bother giving you a “Close all background apps” button like android does. It just automatically closes background apps.) It closes it without warning, and the app is forced to refresh the next time it is opened. The app maker has zero control over this; It’s something the OS does automatically.
So maybe you swipe away to do something small, and your comment is fine when you return. But maybe you swipe away to something more memory-hungry (like maybe you want to go grab a video link.) Now your phone goes “oh hey I need a lot of memory. Time to dump some background apps.” And so even though you were only gone from the app for a few seconds or minutes, the phone still purged it.
Could it be fixed? Yeah, probably. AlienBlue (the precursor to Apollo) solved it by saving your progress occasionally, but that had problems of its own. For instance, your cache would eventually balloon to massive sizes, and it also caused excess power drain from constantly writing to your phone’s memory.