I assume this blog post is targeted for the security community, where IoC is universally understood. Of course it is confusing on HN, but authors are free to assume their audience - like we don't define what HTTP, MVC and "btw" mean every time we use it. Or, for a better example, HN and YC are used here all the time, but would be confusing for outsiders (and should be defined outside of HN context).