Strange behaviour of insert-sexp-before for nested one-line sexps

[abcdw]

Reported in spacemacs repo: https://github.com/syl20bnr/spacemacs/issues/6788

Description

It inserts new sexp inside previous symbol.

Reproduction guide

• Start Emacs
• Open lisp file with two nested sexps on one line (first (second))
• Place cursor on e letter
• SPC k ( (lisp-state-insert-sexp-before)

Observed behaviour:

(firs ()t
 (second))

Expected behaviour:

(first () (second))

or

(first ()
 (second))

System Info

• OS: gnu/linux
• Emacs: 24.5.1
• Spacemacs: 0.105.21
• Spacemacs branch: master (rev. 0283f64)
• Graphic display: t
• Distribution: spacemacs
• Editing style: vim
• Completion: helm
• Layers:

((auto-completion :variables auto-completion-return-key-behavior 'complete auto-completion-tab-key-behavior 'complete auto-completion-enable-help-tooltip t auto-completion-complete-with-key-sequence "C-m" auto-completion-enable-snippets-in-popup t)
 (ranger :variables ranger-show-preview t)
 lua
 (c-c   :variables c-c  -enable-clang-support t)
 (clojure :variables cider-repl-history-size 1000 cider-repl-history-file "~/.cider_history")
 emacs-lisp java python ipython-notebook html latex markdown org yaml version-control git
 (evil-snipe :variables evil-snipe-enable-alternate-f-and-t-behaviors t)
 semantic gtags syntax-checking spell-checking
 (colors :variables colors-enable-rainbow-identifiers nil)
 spacemacs-layouts)