... passages in which the mainpoint is not at all ... it gets into the point it's trying to ... a key element of the point--for instance, maybe the ... "And given that this point is obviously superior, aliens should ... part of the author's mainpoint: the thing that his ...
I would only refrain from highlighting blocks of text, with the exception of the mainpoint. Instead highlight reference words, as sort of visual checkpoints you can use if you ever need to return to something briefly and therefore know where it will be.