I've heard the stories too. I'm definitely very careful when I do it to have the breaker resting against the frame rail, and I never let it crank - just a quick bump.
I don't feel like arguing with anyone on this matter, like I've done in the recent past.
The first rule of repair is; Don't make it worse.
The problem with the 'wedge a breaker bar in there, and bump the starter' method, is that there's a real likelihood of things going wrong, and damaging more parts, and making things worse.
Besides repairing the after effects of people using that method, back when I worked on cars for a living, I still hear the same stories from former colleagues that have stayed in the consumer car repair business.
The bottom line is it's poor advice, that has a high likelihood of causing even more problems for those that might attempt it.
Use the proper tools for the job. Lots of auto parts stores have the tools for rent for a minimal fee.
I just went through that with a so called " certified Toyota mechanic". The crank bolt came out easily since it was not torqued properly the last time it was installed. I found out he used a chain wrench on my harmonic balancer to hold it and only had a 200 lb. torque wrench to which he said the bolt torqued up to that. The chain wrench gouged the pulleys and he managed to bang up and put a hole in the back of my radiator. Anyway I went off on that guy and he bought me a new radiator.
Unfortunately, there are lots of hacks out there, working as "Certified Mechanics". I don't envy anyone that is trying to find a good Mechanic, but rest assured they do exist.