I've only been here a month, so there is much yet I don't understand, but the terms you mention refer to the size of the bankroll of the account. Minnows have more than $1000 or so, Dolphins ten times that, and Whales more than $50k. Which makes me plankton at <$100 =p.
One thing I can point out is that of the rewards you can see you are getting for the comment I am replying to, my vote is worth less than $.10. A dolphin, or whale with a lower weighted vote, has upvoted your comment.
HF19 really seems to have made things better, but I haven't yet seen the data on author rewards, which is the majority of rewards. Before the fork, 1% of accounts received 99% of author rewards. Even just an order of magnitude greater spread wouldn't completely create a fair playing field, but it would show a dramatic improvement.
There will be some tendency of rewards to be preferentially concentrated, as content is variable in quality, topic, and based on personal and familial relationships. No algorithm will create a perfect 'communist' distribution, because voting should create a meritocracy, and the people voting will differentiate between content based on merit.
I do know things are better now, except that downvotes are still impacting some people whose content is being reward deprived by parties able to do so (whales) for personal reasons, and this issue hasn't been much addressed in the Hard Fork.
While there is a fairness issue, which is magnified in the perceptions of most people, the fact of rewards being distributed at all is a qualitative change from other platforms. This is markedly demonstrated by the scarcity of trolls, because trolls don't get upvoted, and do get downvoted.
Even folks who are generally unconcerned with the pursuit of wealth don't see much point in deliberately avoiding it, which is what trolling effectively is going to achieve on Steemit. One of the things I love most about Steemit is that the quality of discourse is radically different from other platforms, and I think this is the reason.
It is that difference in quality of communications that most inspires hope in me for Steemit to become more than just a yakbox, but a means of political decision making. I feel that all the pieces are available on Steemit, and just waiting for someone to figger out how to assemble them right.
The future's so bright, I gotta wear shades.
Thanks for your reply.