Is there any consensus whether you use should a textwidth of 70 or 80 or any other value when writing text documents such as README, INSTALL, etc?

Using 80 is pretty standard. I use it for code, READMEs, etc. However I do push it back to 65 or 70 for emails, just because if folks start quoting the email, extra layers of quote-markers start making things wider.

-tim

autofmt : text formatting plugin

:set runtimepath+='~/.vim/autoload/autofmt/'
:set formatexpr=autofmt#japanese#formatexpr()