comment-multi-linecomment-multi-line is a variable defined in `
newcomment.el'. Its value is
nilDocumentation: 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 C-M-j. However, if you want this behavior for explicit filling, you might as well use M-x newline-and-indent. You can customize this variable.