Do you think your considering HN a clear exception to being “Reddit with a sense of grandeur” might have more to do with your vantage point than your ability to gauge the value of online communities?
It has everything to do with the simple fact that HN was launched in '07, when Reddit wasn't that mainstream.
I consider HN a clean exception to most (all?) online communities in which I have been participaing; in all other cases, the quality tanked, they became ghost towns, or they just changed from their original goal.
Sure, there are many wonderful forums and special interest groups, and it is good that new ones have been created. Just HN is not something you start at, it is something you become.