The goal of peer review is to check the accuracy of the paper's argument. However, I often have so much trouble reading the paper that I can't figure out what the arguments are, much less check their accuracy. This is frustrating. It makes me spend a lot of time re-reading papers.
I've been thinking about clarity in writing ever since my sister linked me to Hemingway App. It's an online application that judges the readability of a passage. It also suggests where sentences may be too long or involved. Simply editing the demonstration passage was a small epiphany for me, as I realized that sentences could be short.
If you write scientific papers, and if you hope others will read them, I suggest you take a look at Hemingway. You might think twice before writing a sentence that spans four lines.
(Hemingway rates this post as at a 9th grade reading level. Experts recommend writing for the public at a 9th grade level at most. The average @real_peerreview abstract seems to rate at a 20th grade reading level.)