I gather that, from the acafan perspective, the "heavy" meta on LJ/IJ is relaxing--after all, there's (usually) no detailed quotes with references, no long paragraphs explaining why each point is relevant to the topic, no introductory section justifying why the topic is worth discussing at all. No abstract.
They're posting often off the top of their heads, sometimes after discussion/beta with a friend, but not with the pressure of "this must be right or it won't be fit to be seen"--they know it'll be okay even if it's unpolished around the edges, or if they mention aspects they're unsure they can entirely support. Which makes it "not really academic" to them.
To those of us with limited or no experience with academia proper, these "non-aca" posts still taste academic. They are often strongly shaped by the academic background of the writer; there's a way academia forces people to write, and therefore think, and that comes across. And to fen who've had strongly negative experiences with a couple of academics (which can include non-fannish academics who are contemptuous of all fandom), that "flavor" can make the whole post come across as condescending and exclusionary.
(This is going somewhere. I think.)
To the non-aca crowd (where sometimes I ID myself, and sometimes not), being told that what they thought were intense, thoughtful, research-laden posts were instead "just kinda musing" can be intimidating as hell. "If that's what she thinks is rambling, then obviously my posts are just baby-babble. I better not say any more on the subject." Some aca-fen are better than others at soothing that kind of worry.
Incompatible memes... hmm. Hotboiz-squee is not incompatible with acafandom, but wanting to not have anything other than hotboiz-squee, is. Non-acafen may not want to hear about "that actor is a sexist pig" or "that show is entirely derivative of this much better show that was canceled halfway through its first season in 1982" or "the director made that scene focus on his naked abs as part of the marketing promo for Tan-Glo™ that sponsors the show;" aca-fen are often willing to discuss those aspects in addition to "OMG could they rip his shorts a bit more? Please?"
And the claim that the squee is one thing, but the aca is "more"--rather than "other"--can be grating.
And I don't think "boysquee vs aca-analysis" is the only conflict; it's just the easiest example to use. Discussing aca-interp vs How My Local Gaming Group Uses This Show And Why That's Fun For Us takes a lot more vocab. And while I'd love to say, "insert other non-aca meme of choice for /hotboiz/," I think I'll have to expand on that idea a bit, because I don't think it's obvious what other options there are.
Because--heh--nobody's analyzing those. Nobody's doing critical deconstruction of non-academic approaches to fandom, because hey, that's kinda the definition of "non-academic."
I think some of the problem is acafandom not acknowledging approaches they don't know exist because they haven't been phrased in a style that (some? many? most?) academics recognize as "A Real Label." And I probably need to split this into two comments, 'cos I feel a religious tangent coming on.