There are "From my campaign to yours" side bars in Ptolus and Barrowmaze. They're interesting and occasionally useful. The problem is referencing the useful ones can be hard. Memory confuses them with the body of the functional text and tends to think of side bars as fluff, and they become a blind spot when you're scanning for something.
Also, no shade on Ptolus or Barrowmaze, both of which have been excellent, but side bars, shout outs, footnotes etc. often seem like self indulgence on the part of the writer to me as a reader. I wish I could put my finger on why since I usually enjoy taking a look behind the curtain, but I've been making an effort to remove references to myself or personal comments from my module writing as a result.