I didn't actually say that I'd not notice a difference in packweight of 1kg. I can feel the difference between a days food.
But with the majority of backpacking loads* it's at most a 10% variation either way.
Not really a 'make or break' the trip, quantity?
It must have been this that confused me
In reality, after a few days, as portion of packweight I'd hardly notice whether my shelter is 1.8kg or 1kg.
Regarding the first quote, I think we kind of agree. I would never make weight the sole or main criterion in choosing a shelter - the Swiftline goes on more trips with us than the Duplex but weighs nearly twice as much. But if both are equally suitable for the expected conditions, guess which one we choose. So I get the search for a lighter tent
IF it will satisfy the other needs you have in a shelter, and you can afford it. And if the lightest tent that meets your needs weighs 1.8kg, you have to take a 1.8kg tent.
Slightly off topic, it's the longer trips where the extra weight would bother me as the food and water would be putting me nearer to where the total weight would indeed be getting to "make or break". On those trips, I'll look to minimise weight where I can, missing out on a few comfort items. On shorter trips I have more leeway for a heavier pad, better pillow etc.