Variable: comment-multi-line
comment-multi-line is a customizable variable defined in
newcomment.el.gz.
Value
nil
Documentation
Non-nil means comment-indent-new-line continues comments.
That is, it inserts no new terminator or starter.
This affects auto-fill-mode, which is the main reason to
customize this variable.
It also affects M-x indent-new-comment-line (indent-new-comment-line). However, if you want this
behavior for explicit filling, you might as well use M-x newline-and-indent (newline-and-indent).
Probably introduced at or before Emacs version 26.1.
Source Code
;; Defined in /usr/src/emacs/lisp/newcomment.el.gz
;;;###autoload
(defcustom comment-multi-line nil
"Non-nil means `comment-indent-new-line' continues comments.
That is, it inserts no new terminator or starter.
This affects `auto-fill-mode', which is the main reason to
customize this variable.
It also affects \\[indent-new-comment-line]. However, if you want this
behavior for explicit filling, you might as well use \\[newline-and-indent]."
:type 'boolean
:safe #'booleanp
:group 'comment)