Usually with K&T comes a whole bunch of other problems.
Agreed, but it's generally NOT the original K&T.
Sometimes it's plumbing though, with pipes touching both hot & neutral.
And the one that bothers me the most is K&T in insulated walls. That can lead to overheating and be dangerous.
I disagree. In four western states, insulating over K&T is legal if first inspected, and a sign getting placed in the access point if any.
But why would anyone think it's dangerous?
If the K&T wire is 12 gauge, and the breaker is 20 AMP, then the amount of heat rise in the K&T will be less than the equivalent modern wire, where the conductors run bundled together. The risk of a nail creating a hot spot is far less with K&T. The K&T uses soldered connections, thus lower resistance than modern wire nuts. Where's the heat risk? Do you have any references to an actual overheating situation in an inspected K&T system with the right protection device installed?
And the one that bothers me the most is K&T in insulated walls. That can lead to overheating
Insurance companies won't insure buildings with fuses and K&T wiring.
Right, but remove the fuses which ARE dangerous, an the K&T fades as an issue for many insurance companies.
Just about every fuse building I inspect has the wrong size fuses in the sockets... generally 30's on 12 or 14 gauge wire . That's not the fault of the K&T, that's the fault of the design that used the same socket for all amperages.