To a first approximation, I think you can gauge how much people think about software quality by how highly they value deletion. While most rookie developers are chiefly interested in building rather than in tearing down (for what I hope are obvious reasons), great throbbing brains like Graydon speak about deletion with the kind of reverence that I presume cardinals reserve for only the coolest of popes.
In what history will likely judge as a vain attempt to impress him, then, I recently landed bug 513147, deletion of the now antiquated “Properties” dialog that used to be available on right-clicking things like images and links. Not because it was useless (every feature is someone’s baby, and is added for a reason) but because it wasn’t useful enough, to enough people, to justify the cost.
50kb of code in our product that is poorly understood, not often used, and not covered by unit tests is not free. When bugs show up, it takes longer than it should to fix them. If a security bug were to show up (which is always a risk when content mixes with chrome, however remote it may seem) it would be particularly expensive for us to reload that context into our brains to fix it.
Deleting it isn’t free either, of course – there are 4 extensions that build off that dialog that will need to be updated, and there may be some who use it regularly who will be disappointed. But the forces of software (inertia, squeaky wheels, cynicism and inertia) bias so heavily towards keeping code in the tree that we should all try to take clear deletion opportunities when they come up. Not capriciously, not without sensitivity to the impact it can have, but with recognition that the hidden cost to keeping them is also large and… hidden.
It is in the spirit of this sensitivity that we, on the Firefox team, have tagged this bug and others like it: [killthem]. What else do you think should go? (And please, be gentle. Remember, every feature is someone’s baby.)
[Update: Geoff Lankow has taken the code that used to be built in, and made it into an add-on, which is think is fantastic. As I said to him, and as I said above, my assertion has never been that the code was useless, just that it wasn't useful enough to justify its cost in the core product. An add-on is a great place for functionality like that, and I thank Geoff for his work.]