One more college student here. You make a few mistakes with your reasoning, but at the same time there's something valuable in your sentiment. The problem with your "baseline platform" is that it runs counter to both how culture forms and to how we process information.
First things first: there is no such thing – none, zip, zero – as raw information. Everything communicable is subjective. That subjectivity might expose objective fact, but even then, there's a subjectivity in which facts are brought up, how they're discussed, and ultimately what facts the communicator knows. You can't separate medium from message. That applies to everything. Rhetoric and information are inseparable.
Your "read everything in your favorite theme/font" assumes that the purpose of publishing is readability, when publishing is just as much about contextualization and "experience-crafting" (too tired to think of the right word). The publishing process lets people decide whether something looks like it'll be worth their time, and it does that in part by creating a certain experience around media consumption that frames the media in question. This process doesn't start when somebody themes a blog or calls an agent. It starts the moment you begin to try to express yourself. There is no such thing as communicating without an audience; every form of communication is a form of publishing.
It's through this process, moreover, that culture forms. From our specific choices we notice and abstract what we believe to be our values. These values then define both how we choose to function within society, and as these values spread they become our society. This is as valid online as it is anywhere else. Gaming theorists refer to a "magic circle" which divides a virtual world's reality from any other; a book I'm reading, Communities of Play, follows online gamers who are forced to migrate to a series of other games, and studies how the values they developed in one game influences their behavior in other games (and watches them try to recreate the original game in scriptable environments like Second Life).
You talk about "authoring" and "commenting" and "sharing" and "upvoting" and, hell, even "editing" like these are all concepts everybody agrees with. But look at the difference in culture even between near-clones like Hacker News and Reddit. Then look at the difference between these sites and sites that are only slightly different – Newsvine, MetaFilter. By the time you get to something two steps changed – 9gag, say, or traditional web forums – you're looking at an entirely different way of processing information, even though you're still looking at essentially the same systemic process. And that's before you look at sites with entirely different purposes. None of those sites have remotely the same purpose as Flickr, and Flickr has little in common with Instagram, and Instagram has nothing in common with, say, TheSixtyOne.
Look, if you're a biochem major you ought to understand that minute variations on a micro level leads to profound changes on the macro. Saying that information can be broken down into text/images/video is like saying that life can be broken down into carbon/hydrogen/oxygen. The magic is that a few basic building blocks can lead to ten thousand variations on the same silly theme, as you say. That's not a bug. That's a feature. I'll take that a step further and say that the magic of computers is how they allow ANYBODY to program systemic processes, so we're seeing systems and cultures evolve that literally never could have existed before. Cultures that rely on passing information that never could have been passed before. That break all preconceived notions of how cultures can exist.
From this baseline computing platform came web sites, a primitive but effective way of creating localized systems. From these web sites came cultures – cultures within sites but also between them, like Communities of Play addresses. The web site is still among the most basic ways for people to publish. I'm publishing my thesis this year as a web site, because I can do things with hypertext and javascript and css that I could never do with paper. The book version of my thesis will be the deprecated version in a number of ways. Does that mean the web site is the only way to publish within these systems? Of course not! Newer and cooler things will evolve with time, and people will rely on the World Wide Web less and less and less. But the WWW is a great equalizer. It's given rise to voices that never could speak before.
Protip: if you're feeling frustrated with the "ten thousand variations", stop reading tech news. Stop reading your Facebook friends. Take control of what you read. Don't rely on fucking Prismatic – it means well, but ultimately it's a hedonistic system, designed to show you what you want and hide from you everything else. Hell, don't rely on ANY recommendation systems. No Hacker News. No Reddit. Look for individuals. Search for people whose voices make you think. Create your own magic circle, your own tiny culture. Don't bother coming up with a platform or a startup to contain that culture. Just make the culture, and then build tools that help that culture sustain and extend itself. Maybe it'll never become huge, but it'll be big enough for you and all the people who think like you, and those are all the people you need. That's the purpose of a culture, after all.
I don't check Hacker News very often now (for reasons just stated), but if you'd like to talk about this more shoot me an email (i.am@me.com). I love having this conversation. Or just talk around this subthread without me, whichever. Fascinating, isn't it, how each thread in a conversation like this becomes a whole culture of its own...