One example of such a play is "splitting tens." That is an agressive play that's usually foolish, except when someone is "card counting"? When suspected, card counters are "barred" from casinos (or worse).
Card counters are usually identified by wildly changing their bet sizes. (That's mostly how they make their money, but they can make "a little" extra money by using card-counting to inform their play). Suppose someone "split tens" without making large bet variations. Would he still be "suspect?"
BTW, what is the rule for splitting tens? Do they have to be the same denomination (two tens, two jacks, etc.) or merely of the same value (e.g. king and jack).
Years ago, someone was harassed by casino authorities for hitting to an 18 and catching a 3 (usually a bad play that made 21 this one time). Upon questioning, this person told the casino that the dealer had a "tell" that said the dealer had 20, so the "heat" went on the dealer, not the player.
Could a player get into such trouble today under the new rules (the dealer is not supposed to look at his "hole" card, but merely turn it up after all the players have played)?
What other kinds of plays may draw "heat" and why?