I both agree and disagree with you on this interesting subject, though you sounded good on this song. Obviously if a key is wrong for a person it is gonna sound bad, and of course I don't want anyone to damage their vocal chords from straining. Use common sense is what you're saying. Proper technique is also a key factor of course, which even many superstars don't use. In a solo situation like this changing keys is not as big of a deal, but in band situations, it can be a huge headache, if you learn the parts, especially the instrumental solos, and a singer comes in and wants to sing it in a different key. I've been in disastrous situations with that over the years in bands. Also, some songs just sound "right" in a particular key, I can't explain why, the tone is just correct, and in a different key, they always sound off. Other songs it doesn't seem to matter at all, baffles me, but I've noticed it. Also, I'm not advocating straining ones voice exactly, but sometimes to stretch it out a bit to reach for a note is a good thing, can help with the projection, and confidence, and some songs need that "oomph" to "sell" the song properly I think, again, other songs don't need that. And just for me, sometimes it's just a challenge to see if I can do it in the original key, and a lot of times I do, but I move keys up and down a lot too, so it's not like I'm married to it, or find it sacred, but there is some merit to it. I find this to be an interesting subject, thanks for bringing it up.