One of the things that frustrates me about academic writing in general is all the obligatory BS that has to go into it
I think one of the aca/non-aca clash points is based on that obligatory BS, which is sometimes left out in LJ/IJ discussions--the acafen want to relax a bit, and so they leave out the "explain terms and lead up to why I'm bothering to make this point at all" section that's the first third of an academic paper... and the non-aca readers who can't keep up and fill in the gaps are left out. Sometimes they just feel a bit lost or overwhelmed; sometimes they feel actively excluded.
And I don't think any rudeness is intended in that, although sometimes the comment exchanges as a result of that feeling get a bit harsh.