A check box "Auto indentation" would be handy to temporarily switch off auto indentation, for corrections
of some strange lines. It could be accessible in the status bar.
It would also solve problems of unwanted indentation implicated by edit modes.
Where should it go? I think as a buffer option.
Also, see these tracker items:
#2962106
(https://sourceforge.net/tracker/index.php?func=detail&aid=2962106&group_id=588&atid=350588)
#2964714
(https://sourceforge.net/tracker/?func=detail&aid=2964714&group_id=588&atid=300588)
#1593607
(https://sourceforge.net/tracker/index.php?func=detail&aid=1593607&group_id=588&atid=350588)
Done in r20191.