Set a minimal character comment limit in Wordpress.

minimal-comment-character-limit.php

<?php
add_filter( 'preprocess_comment', 'minimal_comment_length' );

function minimal_comment_length( $commentdata ) {
    $minimalCommentLength = 20;

	if ( strlen( trim( $commentdata['comment_content'] ) ) < $minimalCommentLength ) 
        {
		wp_die( 'All comments must be at least ' . $minimalCommentLength . ' characters long.' );
        }
	return $commentdata;
}	
?>

Paulund, where is the place where I can put the exact number of letters so that the snippet can work?

@espellcaste Set the $minimalCommentLength variable to a number of your choosing. Example: $minimalCommentLength = 30; to set the minimum comment length to 30 chars. Replace the already present line.

@bungeshea Thanks for answering that didn't realise @espellcaste left a comment.

if the commenters put comment below the certain length, what will happen?