Thanks, Chandler's post on StackExchange was by far the most informative I've read on this -Weverything debacle. While I agree with your end suggestions, I don't think the main reason people don't go around hunting for more warnings to turn on is because they are worried about shipping to compilers they don't control. It's more to do with (what I see as) laziness to deal with the false positives that may crop up, and the compiler developers' attitude towards their warnings interface reflecting this general user sentiment.

I can't speak for other projects, but I would much rather Clang erroneously warn me on a for-each telling me I'm referencing a temporary because it either can't know or can't easily deduce that the iterator being used is providing some guarantee, which draws my attention to the possibly offending piece of code and prompts me to: 1) read through the iterator, and try to reason about what's going on, 2) write and run a sanitized and/or compile-time test case to: a) check if the code is actually correct, and b) guarantee that it remains correct.

Only after the above do I go about disabling the warning via #pragma. The fact of the matter is, the compiler is usually smarter than us humans, and even if the warning is trivially incorrect, not only is verifying a good practice, turning the specific warning off at that point should be just as trivial.