comment-set-column is an interactive compiled Lisp function in `newcomment.el'.

It is bound to C-x ;.

(comment-set-column ARG)

Set the comment column based on point.
With no ARG, set the comment column to the current column.
With just minus as arg, kill any comment on this line.
With any other arg, set comment column to indentation of the previous comment
and then align or create a comment on this line at that column.