!2 Comments.
#
# This is a comment
#
You can add a comment to the wiki markup text by simply putting the '#' sign as the first character of a line.  The entire line, including the line end, will be ignored.
{{{#
# This is a comment
#}}}
There is a slightly different behaviour when you put the '#' sign in front of the first row of a MarkupTable.

See the [[Comment Acceptance Test][.FitNesse.SuiteAcceptanceTests.SuiteWidgetTests.TestComment]]