alt Hacker NewsMaybe the subset of japanese content I'm exposed to is biased, but personally I encounter doubled vowels (obaasan) more often than macron vowels (obāsan). The latter is explicitly "modified hepburn romanization". Even if the latter is more common in general, it's worth noting that the former is the original. The article seems to say that the former is weird and nonstandard, which afaik is completely false.
Also, the particles は を へ aren't always romanized the way they're pronounced; I can think of several places I've seen を written as wo despite being used as a particle.
Using doubled vowels instead of diacritics is just one more concession to Americans, who are unfamiliar with the use of diacritics and whose software frequently does not work correctly when text contains characters with diacritics.
Hepburn is an inappropriate method of writing Japanese, which nonetheless has become the dominant way of writing Japanese, just because it caters to the inability of most Americans to learn how other languages than English are written and pronounced.