Some things that bother me:

Pluralizing with apostrophes.  This is wrong.  Don’t do it!

The singular “they”.  Oh, I know where this comes from: cowardice.  You don’t want to come across as sexist, so you pick a “gender-neutral” pronoun and hope for the best.  Look, if you’re going to pull this dodge, at least do your readers the courtesy of reworking your sentence into a plural form.  Subject/verb disagreement grates on the mind.

Singular “they” is particularly amusing when you do it to hide information, then lapse halfway through your story.  For example:

A student came to my office hours with a simple algebra question: they couldn’t figure out how to apply trig identities to one of the geometry problems in the homework.  As I worked through the problem with them, he got increasingly frustrated, and eventually I realized that he had no intuitive grasp of what the cosine function meant.

Whoops.

“None” as a plural.  No, “none” is a contraction of “not one”, and is therefore singular.  Everybody does this, but that doesn’t make it acceptable.

“Hopefully”.  It’s an adverb meaning “full of hope”.  It does not mean “I hope that…”.

Excessive obscenity.  Heh, just kidding.  Foul language doesn’t bother me at all.