For example, today I read a filing where the attorney REPEATEDLY used "Plaintiff's" when he meant "Plaintiffs." Once or twice I can forgive. I often type a possessive when I mean a plural or plural possessive. It happens. Usually I catch it about five second after I type it or catch it on editing.
But an ENTIRE legal filing with apostrophe abuse?! If I were a clerk, I would be immediately prejudiced and biased against that party. It's not okay.
Also? This attorney repeatedly failed to capitalize a proper noun. Not just any proper noun, but the party's name! Oh my God, make it stop.
The other thing that sets me off? COURT OPINIONS with improper citations. I'm not a huge stickler; if a court uses "Cal. App." instead of "Cal. Ct. App." it's not a big deal because you know what court they're talking about. But "N.J. Super." is NOT okay, because I DON'T know which court that is. Is it the New Jersey Superior Court appellate division, chancery division, or law division? THE BLUEBOOK TELLS YOU HOW TO CITE EACH, SO JUST DO IT.