Using https://developer.apple.com/reference/uikit/nstextstoragedelegate/1534375-textstorage?language=objc which is documented to allow changing attributes

cocoasux.m

// I'm not using the passed editRange and delta because I've found them to be quite misleading...
// This happens to be a new API (macOS 10.11) so maybe it's not really battle tested or I don't know what I'm doing
// Either way I'd like to support older systems so for portability sake it's easier to not use these parameters
- (void)textStorage:(NSTextStorage *)textStorage didProcessEditing:(NSTextStorageEditActions)editedMask range:(NSRange)editedRange changeInLength:(NSInteger)__unused delta
{
	if ((editedMask & NSTextStorageEditedCharacters) != 0)
	{
		//[self updateTextProcessingForTextStorage:textStorage];
		//NSLog(@"Edited range: %lu, %lu", editedRange.location, editedRange.length);
		[textStorage removeAttribute:NSBackgroundColorAttributeName range:NSMakeRange(0, textStorage.length)];
	}
}