Ether won't damage a diesel if used properly, BUT if you have glow plugs, DON'T use ether, you'll might be testing your head bolt's strength or your hood latch.
We used ether on our farm tractors all the time and it never damaged an engine.
Here are a few safety items to remember when using ether.
1. Remember, it is very volatile, don't smoke and beware of sparks.
2. IF possible, have a person help you when starting the vehicle, have one person start the engine, when it is turning over, shoot a small shot of ether in the air intake. Once it has started, DO NOT shoot any more ether into the engine, this is when you can damage an engine.
3. Remember, if the glow plugs aren't disconnected, don't use ether. I heard of someone in the 80's tried to use ether on their diesel engine with glow plugs and it blew the cylinder heads off of the engine.
Myself, I've never heard of using WD-40 as starting fluid, it may work but remember, you'll be leaving an oily residue in your turbo and intercooler.