Is this usage,"could have hardly been more different ", standard and easy to understand for native English speaker? After reading the blog, Kildall and Gates are probably very different, but Google translate means they are the same except "wonderful hackers".
to hardly be more x
to hardly be less x
to hardly be as x as y
examples with other verbs: can hardly be more different can have hardly been more different may hardly be more different should have hardly been more different
hardly is the same as scarcely here.
Hardly ever, rarely, scarcely, seldom Hardly ever, rarely, scarcely and seldom are frequency adverbs. We can use them to refer to things that almost never happen, or do not happen very often. They have a negative meaning. We use them without not. Rarely, scarcely and seldom are more common in writing than in speaking: Cambridge Dictionary
otherwise is often used comparatively: These tables are black, brown or white. Otherwise, their shape and size is exactly the same.
otherwise= in all other respects