I found the solution:
- (void)keyboardDidShow:(NSNotification *)notification {
NSLog(@"Notification: %s", __PRETTY_FUNCTION__ );
//
CGFloat textviewBottom = CGRectGetMaxY(self.commentsTextView.frame);
CGRect belowTextViewRect = CGRectMake(0, textviewBottom, 350.f, self.scrollView.contentSize.height - textviewBottom);
// NB! This works ONLY: 1) keyboardDidShow 2) Non-animated;
// Does NOT work: 1) animated, 2) keyboardWillShow, 3) textViewDidBeginEditing
[self.scrollView scrollRectToVisible:belowTextViewRect animated:NO];
}