

Personally, I don’t think I’d be downloading something when I’m incognito. However, I’d be surprised if it self deleted. I think giving the user the option is better, but my point is that if it is a rare occurrence, then perhaps a non persisting option is better (a remember my choice tick box is still an option).
I think it’s less about making it portable to different OS, and more different versions of the same os on different machines with different configuration and libraries and software versions.