This is the definition of an exploit. Obtaining something you're otherwise not supposed to be able to do. The reason why people get bent out of shape of these glitches and bugs is because it invalidates Nightmare and Hard mode achievements because people who "aren't hurting anyone" by exploiting run around with the same achievements as the people who actually played the game without having to exploit and "tone down" the difficulty without the gaming recognizing it.
Exploits effectively put the game on something easier than easy difficulty. Exploits set the game's difficulty at "Watch the cutscenes on youtube to save you time and money" difficulty because you're effectively just walking through the game using them, regardless of the difficulty and challenge associated with it.
"You're not hurting anyone by using this exploit in a single player game" Yes, you are. Because the more people exploit, the more the honest players have to preface anything worthwhile talking about accomplishing in the game with "I also didn't cheat to do it" like it's standard and a given that people will exploit when things get hard.
No sir, no exploits for me and a big thumbs up to anyone else not doing it 
You know, if the game was balanced I would agree with you 100%. But it's not. The game has bugs and things are broken. Want a certain schematic that is drop-only? Too bad you didn't exploit chests respawning, because now you must replay the game, starting over at level 1, over-and-over until you get it.
Or how about this. I work with a computer most of the day and then come home. I want to play the game, but guess what, my wrists ache and hurt. My fingers cramp up. I can't tell you how nice it was, when I was able to dupe crafting materials. Did I dupe dragon bone? No, but I duped the hell out of iron, obsidian, etc. I'd have duped elf root too, just to avoid having my fingers cramp up. Is that balanced? Is that fun? Maybe if I were masochistic I could see the value is saying "exploiting is bad bad and I give a thumbs down to other people"
Or how about bugged abilities, that don't work. But you have to stick a point into the slot just to get further in the tree. Heck, half of the electricity mage tree is bugged or simply does nothing at all. Sure would be nice if they worked am I right? Too bad the game isn't balanced and not buggy. But oh wait, it is.
I'm playing without the dupe glitch, and I can tell you it has ruined crafting for me. I do not have the time, nor my wrists/fingers the youth, to go picking up every single ore. I love the game's story and action combat, but the farming of materials is not fun. It is also not fun when you clear a level 11 area and get a level 6 epic item. If you want level appropriate gear, you better prepare for farmville.