Not a lot of new information in this article. My summary is that there's no way to verify either Israeli claims about the number of Hamas fighters killed or Hamas claims about the number of Palestinians killed. However, the two groups' claims are mutually consistent, with Israel reporting approximately 10,000 Hamas fighters killed and Hamas reporting 30,000 Palestinians killed.
In December, [the IDF] described an assessment that it was killing two civilians for every Hamas fighter as "tremendously positive", given the challenges it faced on the battlefield.
Of course, (30,000 - 10,000) to 10,000 is 2 to 1.
As Arete says in another comment, 2 to 1 is ordinary for urban warfare. It's better than I expected, actually, given how heavily fortified Gaza is.
There's an interesting blog post by a military historian here. In his words,
The IDF claims that they are killing one Hamas soldier for every two civilians they kill in Gaza, a ratio of 0.5, which their spokespeople have claimed is ‘unprecedented in the modern history of warfare,’ but which looking at the figures above is not actually a particularly scrupulous or discriminating ratio – though of course one may well argue the vast differences in circumstances. It is still both far from the best and far from the worst performance for armies operating in civilian spaces.
I'm not endorsing everything he says but I think he gives some good context on the topic of civilian deaths during urban warfare. (IMO he's being somewhat uncharitable to Israel, given that Hamas spent billions of dollars fortifying Gaza in preparation for exactly this and also has an unusual incentive to have civilians on its own side die due to the role of international opinion in this war.)