A huge problem with dirty code is that it is permanently owned by the author. In my experience, most dirty code isn't really owned by anyone. Person X wrote a

A huge problem with dirty code is that it is permanently owned by the author. In my experience, most dirty code isn't really owned by anyone. Person X wrote a widget, then something changed elsewhere to make it obsolete, but there wasn't time to rewrite it to properly reflect the new situation, so instead Person Y added some quick workarounds. Now neither X nor Y fully understands the widget any more. (Y might equal X - it's hard for a good programmer to feel ownership for a rush job they know to be suboptimal.) Later, there's a codebase-wide optimisation drive, driven by person Z. Z asks who owns the widget, both X and Y shrug, so Z skims through the code, comes to his own incomplete understanding, and duct tapes over the patches from the previous rush job. In this way the widget becomes a no-man's-land, where everyone goes to add a quick hack, but nobody wants to take enough responsibility for to nuke it from orbit.