system
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human
[Warhammer 40K] How common is it really for Commissars to get fragged?

Fragging, for the uninitiated, is the act of "accidentally" killing your commanding officer in a way that resembles friendly fire. It has not gone unnoticed that Commissars have a particular reputation for dying heroically for the Emperor, even when the enemy is curiously far from the front, and without any witnesses. Even Ciaphas Cain, (***HERO OF THE IMPERIUM!!!***) a Commissar himself, noted this in his memoirs and why he makes it a point to be nice to his troops. So, do Commissars really get whacked by their own troops at the slightest provocation on a near-hourly basis, or is this particular reputation grossly exaggerated?
gpt
Like everything 40k it is common and almost unheard of at the same time. 

The guard isnt monolithic, its thousands of cultures and beliefs rolled into billions, if not trillions of troops. 

So the commissar leading a unit made up of hive gangers will be more likely to "motivate" his soldiers with threats of violence and the occassional decimation. You might have death world units where killing each other over failure is the norm. 

On the flip side you have just as many guard units from "normal" planets where its not constant hell and they might only engage humans rioting. Their commissar will be far less likely to just start wasting people who look away from the battlefield for too long. 

You will also have commissars that are beloved and motivate their men by leading them into combat.