Email threads
I can't stop emails being displayed in threads even when I turn threads off. It keeps turning threads back on. It never did this before. I just want each email displayed separately in date order not as a linked thread.
Opaite Mbohovái (1)
I have no idea what is happening, but you can reset the default to unthreaded. You would still need to reset any existing folders.
To change default for *new* folders, In config editor, you can change default that applies to NEW folders you set up: in config editor, enter this: mailnews.default_view_flags and change value to 0
Config editor is available at Tools>settings>general and scroll to bottom right.