TIL: 2 extra comment-dwim features

Today I just learned (by accident) a couple of tricks related to`comment-dwim'. The emacs command is bound to M-; , and it has different behaviours  depending on the line, region, and contents of the selection.

Appart from the ovbious behaviour we all know, today I found that:

• Called with universal argument in an empty line, it adds ARG comment markers in the line. try C-u M-; in an empty line.
• In a line with comments, c-u m-; removes the comments. that means deleting the comment, NOT UNCOMMENTING but removing all commentted text and the comment marker itself.