Writing a good optimizing C compiler is quite difficult
Still infinitely easier than for something like C++ though, which means there's not only more bad compilers but also better good compilers.
Also, to expand a bit on the array thing: that's actually a huge benefit when comparing to other languages, since arrays (unpartitioned, sequential bytes in memory) play very nice with caching, which has led to arrays performing better than other data structures even where it's counter-intuitive, like deleting elements faster than linked lists.
For further actions, you may consider blocking this person and/or reporting abuse
We're a place where coders share, stay up-to-date and grow their careers.
Still infinitely easier than for something like C++ though, which means there's not only more bad compilers but also better good compilers.
Also, to expand a bit on the array thing: that's actually a huge benefit when comparing to other languages, since arrays (unpartitioned, sequential bytes in memory) play very nice with caching, which has led to arrays performing better than other data structures even where it's counter-intuitive, like deleting elements faster than linked lists.