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? :)
That's clearly not true with Wikipedia's hostile to new users policies (even with the existance of "don't bite the newbies").
Even creating a username means you have to navigate the username policy, and the two admin boards (one RFC, one noticeboard) for usernames. There are two templates for usernames (and templating new users is pretty hostile). And until very recently the noticeboard had two different sections, a holding pen and the main board. (They've got rid of the holding pen).
Username creation is less hostile right now that it was a few years ago, but that can change at any moment if someone choses to trawl the new username lists.
And it's really inconsistant: depending who's looking at the name the new user may get instantly blocked permanently; may have to go through RFC/usernames, may have to discuss with admins on usernames for admin attention or on ANI, may have to discuss with admins on their userpage, may have to discuss with non-admins on their userpage.