With the kind of writing I do, 99 out of 100 spelling "errors" aren't errors at all. Spell correction is simply incredibly unhelpful for me. I hate the distracting red dotted underline that appears in my native Mac apps.
What system settings can disable this?
I've tried unchecking the available dictionaries, and changing the auto-choose-language vs. specify language ... all through the preferences panel. But even though I've unchecked US English, the system still spell checks automatically with it in apps.