I'm pretty much on side with Don and Toni on this.
As the OP of the question, I'm looking for a very specific yes/no answer and some information as to why (i.e. what's happening behind the scenes).
Here are my thoughts - if it is plain and obvious that the answer does not address the substantive issue raised in the question we should vote to discard it.
I get what Andrew is saying and agree with it, but at the very least, the minimum standard should be to answer the question.
My test for that in this case is simple - the answer did not address the substantive issue of the question and as the OP, I did not ask for alternative solutions. I am therefore suggesting that post for deletion - IMO it actually has 'zero' value in context of the question being asked.
But for me personally, this a 'strict test' - for example, if the answer even remotely 'addresses the question' (as opposed to missing the question completely) and has some value, however minimal, then I'd let the up/down vote system do it's work.
Don and Andrew I know you both to be very seasoned at answering and evaluating questions and answers relating to Joomla! so I don't think we could go wrong with your personal discretion on a case-by-case basis - and more than anything, I think going with your 'gut feeling' is quite alright as opposed to seeking consensus - the beauty of the SE system is that it's built exactly for that.