"There are ways to mitigate this, but since the model was collecting outcomes to create a statistical distribution, rather than a single deterministic number, it didn't need to."

This is the justification the academics used - because we're modelling probability distributions, bugs don't matter. Sorry, but no, this is 100% wrong. Doing statistics is not a get-out-of-jail-free card for arbitrary levels of bugginess.

Firstly, the program wasn't generating a probability distribution as you claim. It produced a single set of numbers on each run. To the extent the team generated confidence intervals at all (which for Report 9 I don't think they did), it was by running the app several times and then claiming the variance in the results represented the underlying uncertainty of the data, when in reality it was representing their inability to write code properly.

Secondly, remember that this model was being used to drive policy. How many hospitals shall we build? If you run the model and say 10, and then someone makes the graph formatting more helpful, reruns it and it now it says 4, that's a massive real-world difference. Nobody outside of academia thinks it's acceptable to just shrug and say, well it's just probability so it's OK for the answers to just wildly thrash around like that.

Thirdly, such bugs make unit testing of your code impossible. You can't prove the correctness of a sub-calculation because it's incorporating kernel scheduling decisions into the output. Sure enough Ferguson's model had no functioning tests. If it did, they might have been able to detect all the non-threading related bugs.

Finally, this "justification" breeds a culture of irresponsibility and it's exactly that endemic culture that's destroying people's confidence in science. You can easily write mathematical software that's correctly reproducible. They weren't able to do it due to a lack of care and competence. Once someone gave them this wafer thin intellectual sounding argument for why scientific reproducibility doesn't matter they started blowing off all types of bugs with your argument, including bugs like out of bounds array reads. This culture is widespread - I've talked to other programmers who worked in epidemiology and they told me about things like pointers being accidentally used in place of dereferenced values in calculations. That model had been used to support hundreds of papers. When the bugs were pointed out, the researchers lied and claimed that in only 20 minutes they'd checked all the results and the bugs had no impact on any of them.

Once a team goes down the route of "our bugs are just CIs on a probability distribution" they have lost the plot and their work deserves to be classed as dangerous misinformation.

"My view on criticisms of the model were that it was more politically motivated"

Are you an academic? Because that's exactly the take they like to always use - any criticism of academia is "political" or "ideological". But expecting academics to produce work that isn't filled with bugs isn't politically motivated. It's basic stuff. For as long as people defend this obvious incompetence, people's trust in science will correctly continue to plummet.

"Here's John Cormack's take on the model, he saw and cleaned up the original version before it was released. https://mobile.twitter.com/id_aa_carmack/status/125487236876..."

If you check the commit history, you'll see that he quite obviously didn't work with the code much at all. Regardless, if he thinks the model is not worthless, he's wrong. Anyone who reviews their bug tracker can see that immediately.