The colloquial definition is “Useless but impressive and flatters my vanity”.
The probabilistic definition is “Observable thing X signals quality A means P(A|X) > P(A)”.
The economic definition is “Alice signals P to Bob by X if the net cost of X to Alice is outweighed by the benefits of Bob ‘believing’ A, and X causes Bob to ‘believe’ A even when Bob takes in to account that Alice wants him to ‘believe’ A.” (note ‘believe’ A means ‘act as if A were true’.)
You’re straw-manning here. Not conceding isn’t the same thing as denying. To not concede something, one just has to omit the concession from one’s writing. But this is just quibbling. The real issue is the attitude, or the arrogance, that LW may have with respect to academia. Nobody wants to waste time justifying themselves to a bunch of arrogant amateurs after all.
Anyway, some web channels where academics hang out:
MathOverflow
LambdaTheUltimate
The arXiv
StackExchange
The N-Category Cafe http://golem.ph.utexas.edu/category/
ScienceBlogs
(Cracked.com probably does a better job of being a smart, general interest forum than Less Wrong, it’s a great deal more popular at least. But being the highest quality popular forum is a bit like being the smartest termite in the world. Specialized forums are where the elite action is.)