I've always emphatically disagreed with sources in debates being worth two points, especially when the most convincing argument is only worth three.
First of all, the reliability of a source is highly subjective, especially in today's political climate.
Second, everyone has their own opinion on what criteria we even use to judge sources. Some voters give sources to one participant over the other just because they used more of them.
Third and most importantly, sources are not always relavant to the topic and/or the arguments being made. Most debates come down to philosophical differences. The entire point of a debate is to argue your point, not ramble off a bunch of links that say you're right.
That's not to say sources shouldn't be judged or that there are not some debates where reliable sources are crucial to the debate, but I find that in most cases it just skews the point total in ways it shouldn't.