{assign var = 'text' value = $params|@current}
<span class="short-comment">
    {assign var = 'shortText' value = $text|truncate:$column.truncateLength:'[...]'}
    {assign var = 'moreLink' value = '... <a href="#" onclick="$(this).closest(\'td\').addClass(\'full-comment\');return false;">show more</a>'}
    {assign var = 'shortText' value = $shortText|htmlspecialchars|nl2br}
    {assign var = 'shortText' value = '[...]'|str_replace:$moreLink:$shortText}
    {$shortText}
</span>
<span class="full-comment">{$text|htmlspecialchars|nl2br}
    &nbsp; <a href="#" onclick="$(this).closest('td').removeClass('full-comment');return false;">show less</a>
</span>