After reading the summary and the summary of the article, I first thought that women's code is generally better:
Our results suggest that although women on GitHub may be more competent overall (...)
The trick is women on GitHub. In the conclusions they quote another study:
Another explanation is self-selection bias: the average woman in open source may be better prepared than the average man, which is supported by the finding that women in open source are more likely to hold Master’s and PhD degrees
Good job at pointing that out. If we are comparing PhDs to less educated people, it's expected that they have better code. That also makes the gender bias against women's code look even worst.
The only problem I have with the article is in the type of submissions part (programming vs non-programming). From the article:
For instance, changes to HTML could be more likely to be accepted than changes to C code, and if women are more likely to change HTML, this may explain our results.
The authors address the first part (they beat men in most languages, but to different degrees), and they didn't address the second: if
Both outsider women and outsider men have much lower acceptance rate than gender-neutral outsiders, but this is the only case where women supposedly are discriminated. IMHO, they should show the raw numbers (the confidence intervals show that they might not be that much), and check the languages that are in this group. If it's mostly