Sorry for my ignorance, but what is the usefulness of undo persistence after a IDE restart? Don't you normally save your changes and finish a piece of work before exiting an DE?

Edit: some great examples in the replies here, thanks! Perhaps I should start using it in editors that support it, never gave it a thought before.

The whole point of undo is that you realize you made a mistake later. If you've done that after you've saved your changes and exited the program, you'd have no expectation of undo still working unless you've enabled this feature.

It doesn't matter whether or not you can think of a reason you would want to enable it, but it should be pretty trivial to do so. Once you've enabled it, it should work.

The article gave 2 examples.

I can give some as well. IDE crashes. Computer reboots at an undesired time. Even if my work is saved, I am not “finished”. I would like my undo history to extend before file / open time.

The reason why this feature is particularly useful in vi-likes is because they are not IDEs. I hop in and out of vi all day long. Depending on the task I might create a new tab, run a command in vi, or exit vi to run it. Vi’s appeal is that it is “just” an editor and your terminal and workstation form your un-integrated development environment.

I often use it to edit system config files, often on embedded devices where I don't have my git credentials setup, or on servers. In these cases we're already not in an ideal world, I don't have good reliable version control or change management in place. In those less-than-ideal worlds, having proper undo history is nice.

Most apps don't have it, so you might not be used to it, but have you never wished that you could undo the changes you made after you restarted the program?

Moreover, the vim history tracking is amazingly advanced. It's almost like a mini version control system. I highly recommend getting to know it.

If your session / computer crashes, for one.