While I'm not sure what "neoreactionary" refers to specifically there are lots of reasons that certain types of liberals see LessWrong as reactionary:

• A somewhat strong libertarian component
• Belief in evolutionary psychology
• Anti-religous (or generally the belief that beliefs can be right or wrong)
• LessWrong's more technical understanding of evidence is incompatible with standpoint theory and similar epistemic frameworks favored by some groups of liberals.
• Those older discussions around PUA where it's presented in a pretty positive light
• Glorification of the enlightenment.

The impression I got from looking at their graph is that a strong libertarian component is enough by itself. It wouldn't be the first time I've seen people consider libertarianism inherently very regressive.

Edit: Originally I assumed that it was accusing Less Wrong of being neoreactionary, but looking a bit around the site it looks like they might be praising it.

It seems to me that the entire discussion is confused. Many people seem to be using the claim that Omega can't predict your actions to make claims about what actions to take in the hypothetical world where it can. Accepting the assumption that Omega can predict your actions the problem seems to be a trivial calculation of expected utility:

If the opaque box contains b1 utility, the transparent one b2 utility, omega has e1 probability of falsly predicting you'll one box and e2 probability of falsely predicting you'll two box the expected utilities are

1 box: (1-e2)b1 2 box: e1b1 + b2

And you should 1 box unless b2 is bigger than (1 - e2 - e1)*b1.