After two passes, today's South opened four hearts, vulnerable. What is your opinion of that action?
South's hand was atypical, but some experts are inclined to use their judgment. They vary their preempts to keep the opponents guessing. Occasionally, an opponent will be goaded into an indiscretion and suffer a heavy penalty.
My opinion of such "tactical" bidding is lower than Death Valley. I would see no reason to "preempt" as South when one opponent has passed and South has 16 high-card points.
True, North has passed as dealer, but many North hands (K Q 10 5 3, 4 3, A 6, 8 7 6 2 for example) would produce a grand slam, and North will pass four hearts in a flash with that. Moreover, bridge is a partnership game, and a super-heavy preempt may impel your partner to make a losing competitive decision.
What happened after South's bid? All passed, and West led the king of clubs. South ruffed, drew trumps and led a spade to finesse with dummy's jack. When East took the queen, he shifted to the queen of diamonds, and the defense took three diamonds for down one.
South's correct opening bid may be a matter of opinion, but his play was wrong. South should discard a spade at Trick One instead of ruffing.
Suppose West shifts to a trump. South takes the A-K of spades and ruffs dummy's jack. He leads a trump to dummy, ruffs a club, leads a trump to dummy and returns the queen of clubs, pitching a diamond. West takes the ace but must give declarer a diamond trick with the king or concede a fatal ruff-sluff.