I design high performance heating/mechanical systems for a living... I'm not just some yahoo in this case, I actually know what I'm talking about ;)
Putting thermostats in a low load hallway is the absolute worst possible thing you can do. the only reason it's done is because most buildings are not zoned appropriately, so they see the hallways as a "compromise", and since the installer USUALLY is not doing any math or even any serious evaluation of the building the system is being installed in, it's not like they would guess any better otherwise. But the right way is to pick the room with the most intense load profile, hit that, and balance the other rooms in the zone if you must. Or, even better, zone in a way that is actually appropriate to the load.. but that's hard to do with traditional forced air and even harder in a retrofit/replacement situation.
It's true you don't want them near the supply vents. but you do want them IN AN IMPORTANT ROOM. Or... as is usually the case... you will never ensure comfort. The wiki makes some sense in some cases but it's the "rule of thumb' answer and it's why something like 80% of people are not satisfied with their heating system's performance. I would say in most cases your vents will be on outside wall areas, floor level, pointing up. put the tstat on the other side of the room, facing the outside wall. Test a location by putting a thermometer there, running the heating system, and ensuring it does not rise in temperature too quickly. or lick your finger and see if you can feel the breeze (less accurate, but another useful data point).
another horrible practice is putting ducts in attics. 90% of the time that's where they go because it's easy. but it's easily a 30% efficiency loss doing that, even with insulated ducts. That is where "conventional wisdom" and 'standard advice' gets you in the HVAC world.
the nest guys are noticing that room for improvement in this industry is huge. mostly because no one with any education has been pointed at these industries for 50 years. Not that HVAC guys are dumb... far from it... but the "best and brightest" all got pointed at 4 year colleges and never again at residential HVAC. If only the guideance counselors had any idea what a good HVAC guy can make....