I do sometimes wonder if weāre not a little too worried about impaction in our captive reptiles. Iām not saying that it never happens or that it shouldnāt be a consideration with things like feeding and substrate choice. But surely snakes end up ingesting bits of dirt and leaves and sticks and the like in the wild. Do they all drop dead from impaction? Maybe? But probably not, right? Certainly ingesting an excessive amount of substrate would cause problems, but little bits here and there are probably not something to be hugely worried about, at least in my opinion.
Personally, I use loose substrate with both my snakes. Part of that has to do with the species they are and the behaviour they exhibit. One is a sand boa, so she needs loose substrate, as sheās fossorial. My blood python also really enjoys burrowing and nestling in loose substrate, so Iād feel kinda bad taking that away from her (even though plenty of people keep blood pythons on butcher paper and the like).
When I feed, I make sure the rodent is dry, so substrate doesnāt stick to it. My sand boa typically doesnāt strike feed, so I just put her warmed mouse on a dish (though she usually drags it under the aspen to eat it, but thatās natural sand boa behaviour, so thereās really no way around whatever small risk may be posed by the substrate). For my blood python, I wiggle her rat over a wide, flat dish, and sheās usually surprisingly good about striking, constricting, and eating it over the dish (if her strike moves her off-target, Iāll just gently move her on top of the dish once sheās constricting it). Also, her usual substrate is chunks of coco husk that are too large to stick to the rodent, so Iām not really worried about her swallowing anything more than trace amounts of dust. In all honesty, I probably donāt even need to use the dish.
I will say that I think worries about impaction are a better reason to feed in a separate enclosure than fears of misplaced feeding responses or cage aggression. From everything Iāve heard, read, and experienced, thereās just no correlation between bitiness and whether or not theyāre fed in their enclosure. A cage-defensive snake is going to be cage-defensive whether fed in the cage or not, and a food-motivated snake is going to be food-motivated no matter where you feed it.
As for impaction, I think thatās more a matter of deciding how much it concerns you personally, and if so, how you want to go about mitigating those risks. There are various methods and schools of thought, and you just have to decide what you feel good about and what works for you. 
Would the amount of heat radiating from your body at a given moment affect the behavior of a snake? For example, if you had been doing something physically demanding, your pulse was elevated, and your hands were sweatingā¦ would that potentially throw off their ability to differentiate āhandā from āprey-on-end-of-tongs-being-held-by-handā? Or if you had just washed your hands with cold water, would that make them less distracting?
I love snakes dearly, but theāI guess āalien-ness?āof feeding techniques has always intimidated me a lot. Even though feeding a whole prey item is actually, in practice, simpler than trying to juggle a variety of foods, supplements, and treatsā¦ it somehow seems like it would be more challenging to work with an animal that has such a radically different metabolism and specific diet. I have this picture in my mind of me offering a f/t mouse, and the snake just staring at me, like: āSrsly? You think Iām going to eat THAT? 
ā 
I know feeding reactions vary a lot, but do you have to sell them on the idea that this thawed-out mouse is fresh, warm, and alive? Or do they just think: āWell, it smells like food, and itās warm, soā¦ dinner!ā?