Since Emacs 30.1, commenting lines in code blocs does not work correctly

[Denis Bitouzé]

Hi,

* Context

- GNU Emacs 30.1
- Org mode version 9.7.11

* Problem

Since Emacs 30.1, commenting lines in code blocs does not work
correctly. As an example, run:

emacs -Q test.org

where test.org has the following content

--8<---------------cut here---------------start------------->8---
#+BEGIN_SRC emacs-lisp
  (defun org-xor (a b)
    "Exclusive or."
    (if a (not b) b))
#+END_SRC
--8<---------------cut here---------------end--------------->8---

Then select lines 2-3 of this file and run M-x comment-region. This will
result in:

#+BEGIN_SRC emacs-lisp
  ;; (defun org-xor (a b)
  ;;   "Exclusive or."
  ;;   (i
     f a (not b) b))
#+END_SRC

I didn't observe such a problem with the previous Emacs version (29.4 IIRC).

Thanks for any help.
-- 
Denis