I personally come to Less Wrong specifically for the debates (well, that, and HP:MoR Wild Mass Guessing). Therefore, raising the barrier to entry would be exactly the opposite of what I want, since it would eliminate many fresh voices, and limit the conversation to those who'd already read all of the sequences (a category that would exclude myself, now that I think about it), and agree with everything said therein. You can quibble about whether such a community would constitute a "phyg" or not, but it definitely wouldn't be a place where any productive debate could occur. People who wholeheartedly agree with each other tend not to debate.

A 'debate club' mindset is one of the things I would try to avoid. Debates emerge when there are new ideas to be expressed and new outlooks or bodies of knowledge to consider - and the supply of such is practically endless. You don't go around trying to artificially encourage an environment of ignorance just so some people are sufficiently uninformed that they will try to argue trivial matters. That's both counterproductive and distasteful.

I would not be at all disappointed if a side effect of maintaining high standards of communication causes us to lose some participants who "come to Less Wrong specifically for the debates". Frankly, that would be among the best things we could hope for. That sort of mindset is outright toxic to conversations and often similarly deleterious to the social atmosphere.