Variable: viper-ex-style-editing
viper-ex-style-editing is a customizable and buffer-local variable
defined in viper-init.el.gz.
Documentation
If t, Ex-style behavior while editing in Vi command and insert states.
Backspace and Delete don't cross line boundaries in insert.
X and x can't delete characters across line boundary in Vi, etc.
Note: this doesn't preclude Backspace and Delete from deleting characters
by moving past the insertion point. This is a feature, not a bug.
If nil, the above commands can work across lines.
Source Code
;; Defined in /usr/src/emacs/lisp/emulation/viper-init.el.gz
(defvar-local viper-ex-style-editing t)