If you are looking for a word processor rather than a text editor (for coding), then here are your best bets.
1)
Focuswriter (rocks: fast launch, easy spellchecking via hunspell and allows you to create 'themes' that customize appearance)
2)
Pyroom ( is a super simple full-screen word prcoessor that has buffers for multiple projects ... fairly featureless with no distractions)
3)
Wordgrinder (mentioned by others in this thread.... simple word processor that uses ncurses -- but takes a bit to get the hang of managing files)
4)
dav-text (or dav-txt) a tiny terminal-based word processor similiar to wordgrinder but arguably better because there is no mussing with ncurses menu
try them all. see what works best based on your needs and writing approach.
all of tthe above can save as plain text... focuswriters saves as plain text, RTF or obt (libre office's format)
Another alternative is
LYX, which is a latex-based layout and document generator. If you are writing research papers or journal articles, it might be worth exploring. But it is not designed to be a pure word prcoessor.