OmniFocus 2 does not obey the system-wide setting for automatic spelling correction when it comes to the notes field. I have automatic spelling correction disabled in the Text tab in the Keyboard preference pane. I reported this bug a year ago after living with it for a while, and it’s on the radar for the development team.
I’m interested to know if anyone has figured out a workaround, possibly with the app-domain setting for NSAutomaticSpellingCorrectionEnabled. As a shot in the dark, I tried defaults write com.omnigroup.OmniFocus2 NSAutomaticSpellingCorrectionEnabled -bool false and had no luck.
OmniFocus doesn’t take the system preference (allowing you more granularity than if it did), but you should be able to right-click in a note as you’re editing it and uncheck “check spelling while typing” to set the Preference within OmniFocus. Is that not working for you? Apologies if you’ve already gone over this with support.
I installed 2.5.1 test (v106.6 r258600) and it doesn’t appear to have fixed the problem.
I disabled “Correct Spelling Automatically” on a particular note, changed perspective, changed back to the original perspective, and found “Correct Spelling Automatically” to be enabled on that same note.