alt Hacker News> Did you mix up your code points there? It's space that's ambiguous, not tab.
Space is always the same width, but tab means a variable number of spaces (usually either 4 or 8, but I've seen 3 before) depending on people's editor configuration.
What makes you say that the space character, U+0020, is ambiguous?
A single tab always indicates (AFAIK, in common usage) a single level of indentation. Whereas depending on editor configuration a single level of indentation could be represented by any number of spaces - commonly somewhere between 4 and 8, but who can say?
Tab never "means" any number of spaces. How it gets displayed varies but the meaning (of any character, not just tab) can only ever be determined by usage, not display choices (at least for any sane way of doing things). Otherwise what would you make of escape sequences or binary files? Or constructs such as a nonbreaking space?
What business does a compiler have worrying about display width? As I said earlier worrying about the specifics of the editor or other tooling would be backwards information flow and a massive abstraction violation. What if I choose to program in a variable width font? (For the record writing that left me feeling disgusted.)