bug#45915: 28.0.90; deletechar distorts org-table

[Tak Kunihiro]

Dear Ihor,

> However, this (delete-char 1) somehow deletes 2!! chars instead of
> 1. This should be some tricky Emacs issue (bug?). In any case, I am
> not ready to dig into what is going on in Emacs. I do not think that
> such problem is going to appear during normal Emacs usage. At least, I
> was unable to reproduce it by other means than your reproducer
> function.
>
> To illustrate the issue, one can use the following version of the
> reproducer. Feel free to report this to Emacs upstream.

(defun emacs-bug-reproduce-45915 ()
  "Reproduce bug#45915."
  ;; (gnus-read-ephemeral-emacs-bug-group 45915)
  (interactive)
  (with-current-buffer (get-buffer-create "*temp buffer*")
    (erase-buffer)
    (require 'org)
    (orgtbl-mode 1)
    (insert (format "emacs-version: %s, org-version: %s\n" emacs-version 
org-version))
    (insert "|   | rownames |
| / | <l>      |
|---+----------|
|   | a        |"))
  (switch-to-buffer-other-window "*temp buffer*")
  (execute-kbd-macro (kbd "M-< C-n C-n C-n C-n C-f C-f"))
  (message "I will hit S-<return>.")
  (sit-for 2)
  (execute-kbd-macro (kbd "S-<return>"))
  (message "I will hit <delete>.")
  (sit-for 2)
  ;;  (execute-kbd-macro (kbd "<delete>"))
  (delete-char 1)
  (message "I will call previous-line.")
  (sit-for 2)
  (call-interactively 'previous-line))

I still see the problem with GNU Emacs 29.0.50 (build 8,
x86_64-apple-darwin21.5.0, NS appkit-2113.50 Version 12.4 (Build 21F79))
of 2022-05-23 with org-version 9.5.3.

I create org-tables and revise these everyday.  On duplication of a
cell, I hit S-<return> often. The problem occurs, with my use case, once
in 5 minutes. IOW point moves unexpectedly once in 5 minutes.

I think that there is an issue in `org-table-copy-down'. However, I
cannot tell what specifically is not good.

Is this issue of Emacs instead of Org?