But I think it may be important to recognize that for this particular discussion one would have to recognize whether the discussion was designed around the "maximum safe deviation" or the "maximum deviation acceptable for check ride purposes."
I agree, I used the word "safe" because that was what my instrument flying textbook used, and that I take it equates to what would be acceptable in a check ride (half scale deflection but no more). Certainly I wouldn't expect to crash into anything just by going slightly beyond half scale deflection.