What's your must-have features in IDE or text editor?

There must be no hints, overlays, suggestions, or predictive insertion of characters as I type. Enabling these distracting features by default is not a fatal flaw, but if I have to spend more than a few minutes figuring out how to disable them, the editor is not likely to get a second chance.

Click a method to go directly to the definition, themes, debugger.

It must be well-documented, extensible, and have good support for Lisp. IOW, Emacs.

Emacs keybindings.

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