No, I vehemently disagree with most of what you wrote. We certainly agree on basic things that tabs do not have a fixed width, and that a "compiler never has any control over (source code) display." (What a bizarre idea; whoever said it did?)
> I'd dispute that the compiler needs to care about where your editor places the left margin.
This isn't just about editors. I well remember green-bar.
> As long as the prefix remains consistent across a given level of indentation then there's no cause for concern.
No, if someone uses 8 character tabs, and then wants to space over half a tab for visual reasons, things completely break. We probably agree that's wrong, and that the answer is some variant of the answer to "Doc, it hurts when I do this" and I maintain the answer is to dispense with tabs completely.
Look the tabs-vs-spaces war is as old as the big-endian/little-endian war, and I am probably older than you. We'll probably never convince each other of any of this. Have a good day.