How can I do Email->populateTemplate() with multiple objects?
In the docu http://doc.silverstripe.com/assets/classes/default/Email_Template.html#populateTemplate
it says we can call it multiple times, but how does the template discern different variables?

Suppose I have

$mail->populateTemplate($pageAuthor);
$mail->populateTemplate($comment);

where both $pageAuthor and $comment have a $Username variable.

How can I let the emailtemplate know when to use what?
I suppose <% control %> wouldn't work?

A possible solution: just collect the vars you want in a new Array with different names and populate the template with that array.

:-)