I think that when our reputations are on the line, that we act much better but also discard the grit and sharp edges that are the catalyst for interest and growth. I believe that we begin to converge on a single, aggregate pseudo-personality that is the most accepted register for communicating within.
Karma points enable this convergence because they are the only metric that we can do data analysis on comment quality, and so build into the various user interfaces.
So we can all think of many combinations of karma and account - 4chan, reddit, hackernews, youtube (which was trying to require given names); The concept of a website displaying account progeny is both an affront to privacy (in both directions) and a remarkable way to improve comment quality, which I make no effort to define.
The invitation only model seems to scale only so far, as all "cool parties" start off cool because only the cool people are invited (cool in this sense means compatible: consider both artificial and natural boundaries such as a physical party of people congregating for social purposes, a private web forum, or even the internet itself, which was initially available to only those that could enter and navigate it). We have euphemisms such as "Eternal September" to connote the perpetual ruining by outsiders infiltrating what was previously more private.
I vastly prefer to allow the unsanitized comments to enter a feed, and root through them so that people are not behaving as though being watched. It's exhausting but because both extremes are allowed to exist, the comments with the highest signal to noise ratio are often the most honest. Anecdotally I have found (exceedingly rarely) the most honest, insightful, or inclusive comments are on a site like 4chan, with the least restrictions and the least incentive to build a reputation (it's impossible). On hackernews, and I know I am projecting, I believe that we artificially act better than we are, on average, because we have something here to lose. A clever post turns into a job reference, or a reference to work becomes discovered by a future boss, etc.
Ultimately I am glad that all of these combinations exist. Losing a cultivated registry of who's who would have an immediate loss of largely high quality comments, but losing the wild west of anonymous bilge leaves us with no place to be our most honest, regardless of how much or how little it contributes.