I used k9mail for awhile until I realized it had sent every temporary draft of an email as I revised something and changed between apps. Was super embarrassing. Hard to trust it now even though the ui seemed great.
(That’s what the bug reference in a reply to this comment is about)
I tried restarting the app/ refresh email threads, but it didn't fix the visual bug. I'm not sure if the bug is still present today as the email thread has been buried down and I couldn't care enough to follow up on it. I'm just glad it didn't actually send my draft when somehow the app displayed my draft version as sent.
Note that I'm not a user of K9, I'm just describing similar buggy encounter with Gmail desktop and its android app. I only noticed this that one time and just shrug it off due to me turning off apps auto update. Usually I only update manually when I really think I need to and after carefully reading each change logs.