First, when zoomed out, outliers in all possible tasks become more common — internet commenting is just a subset for silly folks like me.
Secondly, the emergent human social fabric is built to recognize and amplify outspoken and / or talented outliers, via mechanisms whereby others who {agree, can find utility, can profit} are incentivized to act as amplifiers. The cost function to repeat a message drops precipitously every time it’s repeated (influences status quo). I’m not sure it’s particularly surprising that internet social forums behave by the same rules — and are even optimized to replicate them mechanistically (upvotes).
I mean... not be dismissive, I guess it does strike me as particularly neat that the internet provides a medium for these people to productively share insight and identify new niches where they can potentially add value to the rest of the world. Where would we on HN be without, say, patio11? :)
I agree most actors we see on TV and movies are outliers (even within the total population of actors). I don't agree they are consequently better than most other people at acting. I think they're marginally better, somewhat practiced, but really "into it" as a career.
Likewise, I think you're underestimating how "good" someone is at a thing if they do it all day. It is difficult to not become good at an activity - for some subset of what that activity entails - if you do it all day long. I think most actors are good at some subset of acting and most Wikipedia editors are good at some subset of editing.
If you dribble a basketball all day long for five years you'll become remarkable at the narrow skill of dribbling unless you deliberately try not to. You probably won't get significantly better at the broader activity of basketball, but dribbling will become like walking for you. In the same way, I don't think there is a large difference in the way actors and Wikipedia editors become good at their activities. They just spend a lot of time in a particular niche.
Part of this is also just the options that first-rate actors open up for you as a writer or director that less capable ones cannot. If you think of the performer's talent as kind of a box that you can fit your narrative and emotional depth in, you just wouldn't try to ship something unless you have a box big enough to hold it.
If you have someone like Anthony Hopkins or Ian McKellan on hand you can give them long, baroque speeches and they will nail it. With a less capable actor you would be forced to keep it simpler because most of that stuff might sound corny as hell in less capable hands.