alt Hacker NewsSeveral of the lean GUI text editors are built on Scintilla (https://scintilla.org/), which provides a cross-platform editing component that can be integrated in GTK, Windows or Mac GUI apps. Maybe that has too much bells and whistles for you, since it's both about editing and presentation.
I guess I might be misunderstanding what Scintilla is? Everything I've seen with it has it coupled with native controls, like a winform control or a Qt control. Are you saying that the library can be used, on its own, without a graphical component? If so, that might fit the bill!