Which is the most popular text editor...

The short answer is there really isn’t one. Editor choice is widely varied and extremely personal. Moreover, since you can theoretically write in any language in any editor, it means that there is a lot of room for diversity on a given team. If I were to wager a guess, I’d probably guess the editors bundled with Visual Studio, Intellij or Eclipse as the most popular editor because the better portion of software written is in-house or for small projects.

Beyond that, there are many choices - Emacs, Vim, Sublime, Atom, VS Code and Notepad++ being the top ones.

Disclosure: I’m a die in the wool Vim user.