Comment tag <b:comment> is an instruction to add HTML Comment tag into HTML document to be rendered or not. Comment is not rendered or not visible by anyone, unless their view the page source.
<b:comment> Syntax and Attribute.
BLOGGER XML LANGUAGE
<b:comment render='BOOLEAN'>
TEXT
</b:comment>Usually used to explain or take a note to the related code block, The render value <b:comment> type is boolean {true or false} by default is 'false'. Our Comment code will be served to the page source only if we give value 'true'. So, we can keep our comment in XML blogger editor without worrying for anyone who sees page source code see it.
<b:comment> Examples
<b:comment render='true'>
I'am comment and will present in the Page Source
</b:comment>RESULT
<!-- I'am comment and will present in the Page Source -->Example usage
Non-rendered comments<b:comment>
This is an explanation.
It will not be in the rendered HTML.
</b:comment>
Rendered comments
<b:comment render='true'>
This is<b:if cond='not data:view.isPost'> not</b:if> a post page.
</b:comment>