> Im a firm believer that one shouldn't be allowed to downvote without leaving a comment.

The purpose of downvoting is to reduce the effective signal to noise ratio by:

(1) reducing the prominence of low-quality posts, and

(2) signalling the types of posts the community finds to be low quality, which will then be reduced in prominence.

Commenting increases the prominence of a post, and as such counteracts part of the purpose of downvotes. It may occasionally be warranted to reinforce the other half of the purpose, but generally not.

> I say this because I often get downvoted because people don't understand my point

Just because someone else suggests that as their reason or a possible reason does not mean that is why other people are downvoting you.

> There is also a disappointing trend to kneejerk downvote any comment that disagrees with any of the "famous" (for want a better description) names on HN simply because member "xyz" must be wrong if they're arguing with the famed member "abc"; regardless of whatever point xyz had made.

I don't think that's true at all; I do think that replies to some of the more well-known posters are more likely to get read and, therefore, voted up or down, but I don't see a lot of evidence for the kind of fan-club voting you suggest (I don't think I'd be on the leaderboard if that was the case, since I think even when I was fairly new a fair share of my posts were disagreeing with some of the more prominent figures here.)

> Then there's the amount of times people can get down voted on popular threads just because they dared express and unpopular opinion.

IME, that doesn't really happen. Any opinion on a controversial thread can get downvoted for no apparent reason -- there defintely are people who downvote for shallow disagreement -- but it rarely seems to last if there isn't a better reason for downvoting, and it seems to happen across the space of ideas (I've seen HN be accused of being a left-wing hive mind, a libertarian hive-mind, and a hive-mind of several different other bents; its not any of those, its got lots of different active factions with lots of different views.)

> It gets harder to have an adult conversation when half the time people are kneejerk downvoting rather than posting a rebuttal or simply asking for clarification on why an opinion was formed to begin with.

I'd rather say it gets harder to have an adult conversation when people lack the introspection to realize the reasons that their comments are getting downvoted into oblivion while others expressing similar ideology in a different manner or not has nothing to do with disagreement, or popular poster fan clubs, and everything to do with the quality of their posts.

> There is no other response to that other than frustration.

Yes, there is another possible response and its called introspection and review of the guidelines.

I've gotten posts downvoted, and of those that have stayed that way more than a few hours, the vast majority have deserved it and I've gotten better at not making the same mistakes. Sure, I think there have been some mistakes (but I have seen a lot more cases of posts of mine being upvoted that don't deserve it.)