In my main fandom (though I'm spending so little time in its sites that I wonder why I still call it my main one) the default state is 'no concrit allowed', and one has to explicitly state one wants it. I think in many ways it's worse.

When the people get used to not getting any kind of negative comments at all, neutral ones start seeming negative. There is case where the author was mad because someone had gone 'wow, awesome, I wonder if z'... 'z' wasn't what the author wanted the people to wonder about (it was true, but the author had the hope of deceiving the readers), and so zie almost flounced--a reader had to apologize for the rest to get them to post again. So speculating about the plot is also a touchy subject, even though it's something that used to be very usual, and something the fandom culture likes a lot. Your typo pointing would count as a grievous offence, as well (though it's my understanding that for some lj circles this is also true. No typo pointing at all or in private--depending on the people).

My main point is that... there's no 'one true way' to comment or receive comments. Expectations vary. I'll keep pushing for a set of them that makes it more likely there will be real conversation, because the alternative is just depressing, though.