Just a nitpick, but the article makes a mathematical mistake. In the last paragraph of section 1.2, it says

    For performance reasons, it is crucial to allocate as
    little memory as possible for runLen, but still enough to
    store all the runs.  *If the invariant is satisfied by all
    runs, the length of each run grows exponentially (even faster
    than fibonacci: the length of the current run must be
    strictly bigger than the sum of the next two runs lengths).*

However, fibonacci growth is strictly faster than exponential. In fact, this is why n * log(n) is the lower bound on the number of comparisons a comparison-based sorting algorithm must use: because n! is approximately n * log(n).