From Wikigogy

Renders as
if no comment was typed, this tip will appear:
[: Um, please type your comment text after the vertical bar in {{comment|...here...}}; see template:comment for help using this template :]

otherwise normally:
[: Your comment text here... and please sign it --Your Username 12:00, Day Month Year (CST)... :]

How to use

{{comment|type your comment here, and sign it with --~~~~}}

The vertical bar (|) separates the template name, "comment," from your actual comment text.

The double curly braces, {{ and }}, define the template.

--~~~~ will add your signature and date stamp. Please sign your comment text with this.

Category:Clean up lists all pages containing this template.

More at template