As a longtime Lisp observer, I can't say that I've ever seen Jon Harrop conduct himself as a "heavyweight" in forums unrelated to OCaml, Mathematica, or F#.
The Jon Harrop who used to hang out on the Clojure list is not the same as Dr. John Harrop who used to advocate F#, OCaml, etc.
I asked him and he said "no relation".
Not really: Jon Harrop is the troll and John Harrop probably not.
Ah, my mistake, I didn't notice the difference in name spelling. It was indeed John Harrop, not Jon Harrop, who appeared to vanish from Clojure after the licensing discussion. I should have made my point without reference to individuals.
"heavyweight" was my opinion of him based on his education, demonstrated ability, and publications, not anything to do with his way of representing himself. I found his comments very interesting, informed as they were by his extensive work in other languages.
Jon Harrop is well known for his spamming work in Lisp and Haskell communities.