Comment 1 for bug 220765

xdg-open is broken on Ubuntu, and the suggested change would not improve it.
The whole idea of having xdg-utils is to have a uniform utility that works the same on all distributions.
Now xdg-open honors the BROWSER environment variable, but Ubuntu patches it to use run-mailcap instead, thus introducing two important differences between distributions.
If a utility needs a browser and asks vanilla xdg-open it will get one. But on Ubuntu the patched xdg-open may give some random utility such as
html2text. This means that Ubuntu breaks all such utilities.