system
Given the following post, respond as if you're commenting on Reddit:
human
[40k/Gears of War] Chainsaw bayonets?

Greetings, I am [REDACTED] of the 3rd Stormtrooper regiment of [REDACTED]. 

Recently, I have been tasked to help survey as a pre orders from high command to scout new worlds for which the Imperium will bring into the light of the Empeor.

On one of my surveys, I have met a somewhat backwater world inhabited by both humans (who we guess were colonists before the Age of Strife) and inhuman xenos. Now their weapons are definitely sub par to us, they're just stubbers without many heavy weapons. But one thing did catch my eye. Every gun used by the human forces has a special "bayonet," in the form of a chainsaw.

I propose that we integrate a few of these small innovations to our weapons to help in meeles. However, I'm now wondering, what series of events would have led to chainsaw bayonets?
gpt
There have been rumours of the Emperor's Angels of Death sometimes using such devices, to great effect. The simple fact of it is, however, that such equipment is neither compliant with Imperial Guard Doctrine, economically feasible on the scale of the Imperial Guard, nor truly effective when used by anyone other than the glorious Astartes. The fact that these backwater neobarbarians, clearly lost to the Light of the Emperor, attempt to use such technologies is just another sign of how far and how fast Humanity can fall without His light.   
It is obviously not effective combat doctrine. If it was, you would have been issued the very same when you finished your training.

For the average Guardsman, a standard issue bayonet is more effective, as well as being simpler to clean, maintain and use.