Many, many, years ago a neighbour had a brand new MKII Escort Popular which had a missfire when just a few weeks old. He couldn't get an appointment for main agent to sort out for a week or so and they gave him a set of new plugs to try himself. They were so tight from the factory I had to smash off the insulator and use a socket with long power bar to remove them. They were tight all the way when being unwound so probably already on the way to be stripped threads in a brand new car ! BTW new plugs cured missfire.
Joking aside but in early 70's a mate had a RD250 Yamaha which he stripped the plug thread. He simply Araldited the plug in and then did many thousands of miles without a problem. If the plug fouled he quickly removed the head to clean it !
My 1959 CB92 Benly came off the road in early 60's due to stripped plug thread and I haven't got "aroundtuit" to repair yet
I once popped a plug that had been cross threaded. Was abroad at the time so chopped the sealing washer off and put it back in again with some loctite. (The idea being that without the washer the extra threads would be enough to catch)
Was fine for many thousands of miles. In the end the engine ate itself for some other reason