I don’t know if there is an “issue” with fromIterator, the comment is just that it is ad-hoc: there is no law for it to satisfy.
Law-abiding means that some equation holds, for example a monoid instance should be associative, so ((a <> b) <> c) should always produce the same result as (a <> (b <> c)). There is nothing checking that my implementation of <> abides by this law, but other programmers (and optimisers or compilers, maybe?) can make use of it, and might write incorrect code if my instance does not abide by the law.
Another example would be functors: it should be the case that (fmap f) . (fmap g) is the same as fmap (f . g), for all functions f and g that make sense in the equation (output type of g must match input type of f).
I guess that also explains why all their "help us get to X" have been achieved several times over. Hopefully most of those contributions are actually by serious participants and not just a bunch of trolls trying to poison the database.
This reminded me of Hannah Gadsby's "Nanette" because, like Ali Wong's show, it has a strong narrative arc, and because, like this presentation itself, it analyzes the structure of comedy.
