Hello,

This minor automatically lets you close block comment when typing
a block comment start.

Thus...
#+begin_src
  typing /* in c-mode
  automatically inserts */.

  electric-block-comment-mode: on

  /*|
    ^ cursor

  /* | */
     ^ cursor

  Or in lua --[[ inserts ]]--.

  electric-block-comment-mode: on

  --[[|
      ^ cursor

  --[[ | ]]--
       ^ cursor
#+end_src

and so on.

*However, there is a problem,*
This minor mode uses =block-comment-start= and =block-comment-end=
variables, which most of the major modes do not use or define.

The reason I decided to use these variables is because are more explicit
with the type of comment that is used/supported.

I would like to hear your feedback.