Well, Wikipedia determines this by setting their notability guidelines.
At the end of the day, it's up to each individual community to determine what is and is not appropriate. It wouldn't hurt you if somebody started posting celebrity gossip articles on HN, but HN would probably downvote them into oblivion because it has decided those types of articles are not relevant to this community. I can say with a high degree of certainty that you would not object to this practice. With Wikipedia it's the same principle.
Except the notability guideline is at odds with the stated goal of Wikipedia -- to collect and provide the totality of human knowledge, for free.
Far better would be to do away with the notability guideline entirely. The purpose it allegedly serves is in keeping unverifiable (as in, cannot be confirmed by reference to reliable sources) information out of Wikipedia, but Wikipedia already has two full-blown and actively-used policies regarding that matter. All that's left for notability, then, is to turn Wikipedia articles into popularity contests, something that's definitely at odds with its stated goals.
But who really cares if these pages exist on Wikipedia?
Would it affect the speed of serving up the more desired pages? My heart is with the inclusionists, but would Wikipedia be as easy and as fun to use if its database size were much larger for the same budget?
How are these brief entries any less important than descriptions of the complete episodes of BSG, Doctor Who, The Wire, or dozens of other TV shows? Yes, I've read many of those episode articles and I'm sure they get more hits, but we're talking about making information available to anyone who might needs it. Who can say this is needed, this is not?
It seems odd that a real person can't get an entry but there are probably thousands of fictional characters written up.
You're really arguing not about whether topics should be included in the encyclopedia, but how their articles should be organized. Your argument is placated by reorganizing The Wire into one big article with all the detail from every episode. But the article was broken up not because of some separate notability for each episode (though some of them clearly are, ahem, notably notable), but because it makes WP's coverage of The Wire easier to read.
I don't think his argument is "placated" by that at all -- the point remains that lots of minutiae are apparently deemed worthy of inclusion, while arguably significant real-world people or organizations (which in many cases meet the letter of the law for notability) are not. The "notability" standard is applied very inconsistently, and in a way that seems to boil down to "whatever the Wikipedia brass find interesting." If that's the standard, fine, but be honest about it.
Again, a canard. Notability is far less subjective than it's made out to be. What episode of The Wire hasn't been written about in a reliable source somewhere? Zero, is how many.
Further, WP accomodates a myriad of non-notable facts. They're simply attached to notable subjects. The idea that every single sentence in WP must be notable is a straw-man argument. Once you accept that The Wire is notable enough for inclusion in WP, by nature of being the single best piece of long-form televisual drama ever created, then the question of how its articles are organized stops being about notability and starts being about information design.
And, I mean, have at it and all. But don't make it something that it isn't.
That may be, but you have to admit that there are thousands of fictional characters with larger impact on our world than the majority of real persons...
At the end of the day, it's up to each individual community to determine what is and is not appropriate. It wouldn't hurt you if somebody started posting celebrity gossip articles on HN, but HN would probably downvote them into oblivion because it has decided those types of articles are not relevant to this community. I can say with a high degree of certainty that you would not object to this practice. With Wikipedia it's the same principle.