Have to agree with 411A - it's just an observation of normal line operation and the check captain should not "interfere" with the operation.
Remember that you cannot complain about the result of a check but you can complain about the conduct and if you are being asked all sorts of "technical" questions during the flight then you could (quite legitimately) complain that this was distracting you from the task!!
The debrief is surely the time to highlight any areas which come to light as a result of the observed flight and perhaps, if necessary, probe to see whether there are any areas which require some education etc.
However, my experience of line checks is that the vast majority do a fine job and it's usually pretty obvious to all when there has been a cock-up! Those that fly the line in the correct manner have no need to worry.
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