Hi - have come across this a few times - some of the past suggestions don't work so I thought I'd post an update for how I was able to do this.
Location: wp-includes > comment-template.php
Removing the quoted text along will not resolve the issue. You ened to remove the following lines entirely:
`elseif ( $number == 0 )
$output = ( false === $zero ) ? __('no comments') : $zero;
else // must be one
$output = ( false === $one ) ? __('1 Comment') : $one;`
Hope this helps :)