I found my favourite writing environment (IWE?) to be Vim + Goyo [1] + line-wrapping with j/k keys mapped to gj/gk [2]
[1]: https://github.com/junegunn/goyo.vim
[2]: http://vim.wikia.com/wiki/Move_cursor_by_display_lines_when_...
[1]: https://github.com/junegunn/goyo.vim
[2]: http://vim.wikia.com/wiki/Move_cursor_by_display_lines_when_...
As a side note, I don't like line-wrapping too much, I prefer auto formatting (:set tw=80 and then type away, vim will handle the line breaks)