The article reads more like pr damage control than an actual complaint. epoll has a reputation as a fragile, hard to correctly use interface. and kqueue as relatively simple and sane. So the question always is. why didn't linux just adopt the already existing kqueue instead?
Sometimes it seems that linux does end up with more than it's fair share of technical excellence coupled to a bad interface. iptables, epoll and git come to mind.
Because it discusses epoll in much more detail, it is far more convincing than the parent article of this thread.
The conclusion of that article is that how to use correctly epoll is not at all obvious and it has some pitfalls that are not easy to avoid. Therefore epoll seems to be more affected by a serious technical debt, i.e. by a less than good design of the original API.
Sometimes it seems that linux does end up with more than it's fair share of technical excellence coupled to a bad interface. iptables, epoll and git come to mind.