XF 1.4 Merging Templates


I'm currently testing 1.4, and I need to merge some templates, as I have a very customised theme.

When I select to see the differences it shows different lines in red and green. I assume that I should compare the difference between the two, and I believe the line highlighted in green is my current code, is this right?

So to correctly apply the changes, do I need to update my code to include items in the red highlighted line?

For example in message template, the following line is in red:

<li id="{$messageId}" class="message {xen:if $message.isDeleted, 'deleted'} {xen:if '{$message.is_staff}', 'staff'} {xen:if $message.isIgnored, ignored}" data-author="{$message.username}">
and the line in green is:

<li id="{$messageId}" class="{xen:if $userStatus.userOnline, 'online'}  message {xen:if $message.isDeleted, 'deleted'} {xen:if '{$message.is_staff}', 'staff'} {xen:if $message.isIgnored, ignored}" data-author="{$message.username}">
At the moment the online status indicator doesn't show.

Sorry if this seems a dumb question, I just want to ensure I get this right.