[invalidOrTaken]

Fairly easily? If you're maintaining legacy code, here's what happens: you dive in, are horribly confused, and figure it out. Aaaaaaand...now you know it. Who cares if it took you three days to figure it out? You're going to be maintaining that codebase for a long time, aren't you?

We're kidding ourselves if we believe that our dev work is "all-new algorithms, all the time." It's not.

[johnnyfaehell]

Who cares? Stakeholders who are pissed of the legacy system isn't working and want it fixed now. If it's legacy and you're changing it, it's generally because it's broken and someone finally noticed.

[vonmoltke]

In my experience, cases where the system needs to be fixed right now are fairly rare, and in those cases the task is usually delegated to the person with the most system experience anyway.