Some asked to me, some others did not. Thank you very much to users who are asking before remove. :)

I agree for everyone to HIDE the "powered by JoomlaComment..." part, NOT TO REMOVE.

Hide means to add "display:none" properties. Not to delete lines.

Just add the following line in the css of the joomlacomment template (or joomla template).

#poweredby { display:none; }

To customize (copy...) your template please refer to article 3.20: customize your own template

Thank you very much to respect !