The dumpster truck example was an extreme example. In reality it'll be as simple as someone who does no work coming to the store and taking the fruit of other people's labor. People will resent having to work to produce goods for someone who refuses to work and just takes from them.

They can come to the store as much as they want, but they don't reserve the right to do whatever they want. The commune(s) producing the goods in that store have a good reason to deny someone this. And again, why would someone do this in the first place? This is the question you need to answer first.

Okay. He says he's taking a truckload of produce so he can make a year's supply of pasta sauce. It's not hard to find reasons. I freeze or dry crates full of fruit when they're in season.

Fine, so people will expect a year's supply of pasta sauce at some point? And if they don't get it, that person doesn't get any more? I fail to see the problem here.

But anarcho-communist theory says he's fully within his rights to take whatever he needs and no one else in the community has a right to judge how much he needs.

Erm, no. They're anarcho-communists, not anarcho-simpletons.

<Sharing an undesirable job communally really means very little. The vast majority of jobs are undesirable. There aren't enough volunteers to share all those jobs. Undesirable jobs are the jobs that would need to be maintained in a communist society. Desirable jobs are the jobs that would go away because they're not necessary. Anything necessary is hard work and thus undesirable.

The vast majority of jobs are undesirable in capitalism. There's no reason why they would stay the same way in an anarchist society and not be made to be fun. You have completely the wrong impression on why people do not like working. It's not because the work is hard, it's because of the hierarchies enforced within them. People have no issue at all doing hard work, even less desirable work, just for the recognition of their peers.

And again, works which simply cannot be automated away, or not made more fun (and they will, because necessity is the mother of invention) will simply be communal. It doesn't matter if there's enough "volunteers". Either you do your part, or you're ostracized from the community for being selfish. And trust me, there's very few things more powerful than peer-pressure.