It would be enlightening to hear and see a video of the interview questioning of Hillary by the FBI, where most likely she coughed during the interview. However, the Government chose not to video the interview.
“Interview And Interrogation Seeking The Truth DOD Polygraph Institute”
B. Activities that deceptive suspects engage in to reduce
their tension when lying.
Timing and Consistency Are Critical
e. Clearing of throat, coughing and sniffing.
Good point, but we know the FBI had no intention of getting to the truth. With that many "I don't recalls", it was certainly obvious to them.