I was "shocked beyond belief" to see things like "the fact of the matter" and "high time" and "as luck would have it" circled. I actually thought that such colloquialisms, precisely because of their familiarity, would make my paper "easier to digest" and better "all the way around." (The quoted phrases are trite, of course.) It never occurred to me that perfectly serviceable everyday phrases could actually be a bad thing.
Decades later, I see my professor's point. It's not that trite phrases aren't easy to understand (they obviously are, or people wouldn't use them) but that they're unoriginal, bland, banal, and bromidic. They represent missed opportunities to inject vitality into a piece of writing.
The surprising thing about cliches in English is how ancient some of them are. Many of our most cherished cliches are, in fact, over 400 years old and trace directly to Shakespeare.
- all that glitters ("glisters") is not gold (The Merchant of Venice)
- all's well that ends well (title)
- as good luck would have it (The Merry Wives of Windsor)
- bated breath (The Merchant of Venice)
- a charmed life (Macbeth)
- be-all and end-all (Macbeth)
- better foot before ("best foot forward") (King John)
- the better part of valor is discretion (I Henry IV)
- neither a borrower nor a lender be (Hamlet)
- brave new world (The Tempest)
- break the ice (The Taming of the Shrew)
- budge an inch (Measure for Measure / Taming of the Shrew)
- cold comfort (The Taming of the Shrew / King John)
- come what come may ("come what may") (Macbeth)
- dead as a doornail (2 Henry VI)
- (let slip) the dogs of war (Julius Caesar)
- devil incarnate (Titus Andronicus / Henry V)
- eaten me out of house and home (2 Henry IV)
- elbow room (King John)
- faint hearted (I Henry VI)
- fancy-free (Midsummer Night's Dream)
- fight till the last gasp (I Henry VI)
- flaming youth (Hamlet)
- forever and a day (As You Like It)
- for goodness' sake (Henry VIII)
- foregone conclusion (Othello)
- full circle (King Lear)
- the game is up (Cymbeline)
- give the devil his due (I Henry IV)
- good riddance (Troilus and Cressida)
- it is as Greek to me (Julius Caesar)
- heart of gold (Henry V)
- high time (The Comedy of Errors)
- hoist with his own petard (Hamlet)
- household words (Henry V)
- ill wind (2 Henry IV)
- heart of hearts (Hamlet)
- mind's eye (Hamlet)
- in a pickle (The Tempest)
- it smells to heaven (Hamlet)
- kill with kindness (Taming of the Shrew)
- killing frost (Henry VIII)
- knit brow (The Rape of Lucrece)
- laughing stock (The Merry Wives of Windsor)
- laugh yourself into stitches (Twelfth Night)
- lean and hungry (Julius Caesar)
- lie low (Much Ado about Nothing)
- live long day (Julius Caesar)
- love is blind (Merchant of Venice)
- strange bedfellows (The Tempest)
- Much Ado About Nothing (title)
- naked truth (Love's Labours Lost)
- neither rhyme nor reason (As You Like It)
- not slept one wink (Cymbeline)
- one fell swoop (Macbeth)
- loved not wisely but too well (Othello)
- jaws of death (Twelfth Night)
- flesh and blood (Hamlet)
- star-crossed lovers (Romeo and Juliet)
- what's past is prologue (The Tempest)
- pitched battle (Taming of the Shrew)
- play fast and loose (King John)
- pomp and circumstance (Othello)
- pound of flesh (The Merchant of Venice)
- primrose path (Hamlet)
- salad days (Antony and Cleopatra)
- sea change (The Tempest)
- seen better days (As You Like It)
- send packing (I Henry IV)
- make short shrift (Richard III)
- sick at heart (Hamlet)
- snail paced (Troilus and Cressida)
- something in the wind (The Comedy of Errors)
- something wicked this way comes (Macbeth)
- sorry sight (Macbeth)
- sound and fury (Macbeth)
- spotless reputation (Richard II)
- the short and the long of it (The Merry Wives of Windsor)
- sweets to the sweet (Hamlet)
- there's the rub (Hamlet)
- too much of a good thing (As You Like It)
- tower of strength (Richard III)
- truth will out (The Merchant of Venice)
- wear my heart upon my sleeve (Othello)
- what's done is done (Macbeth)
- a rose by any other name would smell as sweet. (Romeo and Juliet)
- what the dickens (The Merry Wives of Windsor)
- wild-goose chase (Romeo and Juliet)
- the world's my oyster (Merry Wives of Windsor)
- yeoman's service (Hamlet)
Any time you use one of these stock phrases (so original in their own time; so stale in ours), you're joining a centuries-old procession of uninspired writers who've chosen convention over creativity, banality over originality, processed white flour over whole-grain goodness. Plus you're stealing from another writer. I say leave the poor ba(sta)rd alone. He's been plagiarized way too many times.