There are two common objections to Corbynomics (pdf) which seem to be to be misplaced.
I'm not so sure. People's QE is a response to a problem which is perhaps more severe now than in the past - that the UK invests too little. The share of business investment in GDP has been trending downwards for years: complaints about BT's tardiness in rolling out fast broadband are symptomatic of a wider problem. And if fears of secular stagnation are even partly true, it might stay low. Greater public investment is a response to this.
In this sense, it might be Corbyn's critics who are out-of-date. The assumption that the private sector will generate investment, innovation and dynamism if only left alone might have been reasonable in the 90s. But it is in question today - hence, perhaps, a need for greater state activism.
The second objection is that people's QE could undermine the Bank of England's independence because it is, as Tony alleges, "pretty much orthogonal to whether it’s actually needed for monetary policy purposes."
Certainly, Corbynistas have been presenting it that way. But I'm not sure this is right. It's likely that Bank rate would be low in 2020: Mark Carney has warned that rates might peak at less than 3%, and futures markets are pricing in a rate of barely 2%. This means the Bank would have very little orthodox monetary policy ammunition to fight any deflationary shock. And there might will be such a shock not only from ordinary macroeconomic surprises but from Corbynomics itself. He wants big - possibly unachievable - tax rises on companies and the rich. These could well be deflationary. It's quite possible, therefore, that QE would be needed for conventional monetary policy purposes - to get inflation back up to 2%.
In saying all this I don't intend to wholly defend Corbynomics. I'd prefer more emphasis upon decentralized decision-making and worker control than he seems to be offering. And, paradoxically, I don't think he is sufficiently anti-austerity. Talk of people's QE dodges a big fact - that with real interest rates below zero (and expected to remain so) public investment can be easily financed through ordinary borrowing. And in wanting to close the "tax gap", Corbynistas aren't anti-austerity at all; they just think it apply to different people.
All this leaves me in an odd position. I find Corbynomics neither as good as its supporters believe nor as scary as its opponents claim. The strongest case against Corbyn becoming leader might lie outside of economics.