It's exciting to know that potential buyers won't have that worry and that we don't need to do any reassuring or explaining.
I think that it's important to note that knob & tube wiring isn't all bad, though. It's important not to get all bent out of shape about something that isn't commonly understood. Home improvement shows like the ones that run on HGTV will commonly use the discovery of knob & tube wiring as an opportunity to inject some drama into an episode. Or, perhaps, it's the contractor who is capitalizing on the opportunity to milk the homeowner for a larger profit. Or both. But, it almost never fails when the demolition crew "discovers" the knob & tube that the dramatic music is queued up and dollar figures start to get thrown around.
Every home and building built before 1930 that has been wired for electricity has had knob & tube wiring that may still be in perfectly good operation today. Ours was in great shape and could have easily lasted for many more decades of use.
In the shows I've watched, I've seen electricians and contractors explain how the insulation is brittle and can easily expose bare wire when the insulation just "falls off". Sometimes, they even demonstrate this by pulling the wire around. However, wiring should be hidden within the walls or under floors. They shouldn't ever be being moved around. The only way to get dry insulation to crack and "fall off" is to take the wire and bend the junk out of it. This obviously doesn't happen installed and in use and so there is no need for flexibility.
Furthermore, all of the old knob & tube wiring that got pulled out of our house was well insulated and plenty flexible. None of it cracked or fell off even after it was being all bent up to be shoved in a trash bag. And, it's because it was being used correctly. The only way that old wiring can become brittle in the first place is if someone overloads the circuit. That overload will cause the wiring to be resistant to the required flow of the appliance, get hot, and literally bake the insulation on the wire. But, a properly-sized breaker on the circuit would prevent this. Even an old fuse would prevent this. So, if this has happened to any wire, old or new, it's because someone did something irresponsible like put the wrong size fuse or breaker on a circuit.
Once you understand electrical loads and the purpose of fuses and breakers, it's extremely easy to correctly wire a circuit for what is going to be being used on that circuit or what would likely be used on that circuit in the future.
