AHA! Futhermuckerzzzzzzzzzzzzz!!!!!!! Who removed the space then? Itz gone innit. No wonder we haz bugz. 
I'm gonna put it back in, with notez. In bold. 
To be clear, this bit in GenericControls.template.php:
function template_control_richedit($editor_id, $smileyContainer = null, $bbcContainer = null)
{
global $context, $settings, $options;
$editor_context = &$context['controls']['richedit'][$editor_id];
echo '
<textarea class="editor" name="', $editor_id, '" id="', $editor_id, '" cols="600" onselect="storeCaret(this);" onclick="storeCaret(this);" onkeyup="storeCaret(this);" onchange="storeCaret(this);" tabindex="', $context['tabindex']++, '" style="width:', $editor_context['width'], '; height: ', $editor_context['height'], '; ', isset($context['post_error']['no_message']) || isset($context['post_error']['long_message']) ? 'border: 1px solid red;' : '', '" required="required">', $editor_context['value'], '</textarea>
Has to be like this to stop this bug in FF:
function template_control_richedit($editor_id, $smileyContainer = null, $bbcContainer = null)
{
global $context, $settings, $options;
$editor_context = &$context['controls']['richedit'][$editor_id];
echo '
<textarea class="editor" name="', $editor_id, '" id="', $editor_id, '" cols="600" onselect="storeCaret(this);" onclick="storeCaret(this);" onkeyup="storeCaret(this);" onchange="storeCaret(this);" tabindex="', $context['tabindex']++, '" style="width:', $editor_context['width'], '; height: ', $editor_context['height'], '; ', isset($context['post_error']['no_message']) || isset($context['post_error']['long_message']) ? 'border: 1px solid red;' : '', '" required="required">', $editor_context['value'], ' </textarea>
Yes, I know it's a trivial and stupid change, but it works. There ya go. 
However, this leads to another question. Why are $editor_context['width'] and $editor_context['height'] still present? I was sure we killed those ages ago. I'm 90%+ sure they were even killed in SMF 2.1 Alpha, let alone Elk.
These settings are remnants from IE4 days, when no browser supported CSS. If we can't do this without them, we aint trying.