For me, nano was the text editor that I immediately knew how to use. No need to learn, you just read the bottom of the screen, and you can do the basics. For writing a commit message, it's more than enough.

Compare that to Vim: it's a great tool for coding, very powerful, you can easily customize it, optimize it to your needs, but you actually need to spend time learning to use it, and then tweaking it to your work.