If the answer to the question would come from someone who knows Drupal well (without making any other assumptions), then it should be here.
An example of this might be "How can Drupal create Blah the way that Joomla does?"
If the question is a comparison like "Which would do a better job at X, Drupal or Wordpress?", then you might be able to rephrase it as "Can Drupal do X, or should I be using something else?" listing Wordpress as a possible alternative in the body.
However, if the answer would come from for example a PHP/Wordpress expert, like "How do I do X that Drupal does but in Wordpress?" then it would be outside the bounds of Drupal.
There is obviously a gray area, and if it's questionable I don't think it hurts anyone to ask on SO.