I hope the subject line made you cringe.
Current vernacular is appropriate for dialogue in novels, screenplays or in verbal exchanges. Mangled English can give hints as to a protagonist's or antagonist's background, history or culture, or intent. Nothing like injecting a little relatable reality to a story to capture a reader's interest.
Writing as you speak or converse should not be the method used for writing a thesis for college, or a cover letter to go with a resume. There's a certain expectation for correct grammar, punctuation and spelling aptitude that a professor or hiring HR director looks for. No professional report, grant or article, or anything that strives to be professional, will be taken seriously if it is riddled with sloppy grammar/spelling and pop culture colloquialisms.
Readers have the same expectations of a novel - good grammar/spelling but with realistic dialogue. Grammar mash-ups aren't out of place in that venue.
The same cannot be said of a review.
Reviewers need to avoid sloppy writing, especially if you want to be taken seriously.
Should of (should have)
Could of (could have)
Gotta (got to)
Sista or Sistah (sister)
definately or defiantely (definitely)
Your vs. You're
Its vs. It's
Too vs To vs Two (it's happened)
Peek vs. Peak vs. Pique (a common, too common, issue)
Alot - no no no - A. Lot. It's two words. Two separate words. A lot
Be alert for:
Pluralizing words with apostrophe S (throwing pies is load's of fun, his chicken's are breakdancing)
Being too familiar - (Dude, this book knocked my socks off, Sista, you gotta read this! )
Using profanity (This book scared the shit out of me!)
Don’t make nouns into verbs.
Starting a sentence with and/but/or - those go in the middle of a sentence connecting two related sentences, because they are conjunctions.
Forgetting to capitalize the proper nouns in a book title.
Forgetting to capitalize the beginning letters of a sentence.
Forgetting to check the spelling of an author's name, character's name or book title.
I know there are more examples. In fact, I'd appreciate it if visitors contribute their own examples of "sloppy writing" pet peeves. Highlighting them might make mistakes quicker to spot and easier to avoid.