Hands are from Soledad Club, November 5, 2018.
There is a logical reason for the guideline of: “Do not play honors toward higher honors unless you have lower honors to promote.” Today had an excellent example.
West: ♠AK8 ♥109 ♦AJ7654 ♣65
East: ♠Q109 ♥AKJ2 ♦Q8 ♣KQ98
Your contract is 3NT, Declared by East. You get a favorable heart lead and North (RHO) covers Dummy's ♥9 with the ♥Q. You are now guaranteed four heart tricks. You have eight diamonds, and the proper play is a LOW diamond toward the ♦AJ7654 on Dummy. Do NOT waste your ♦Q when you do not own the ♦10 or ♦9 to promote. Proper technique pays off because South (LHO) has the singleton the ♦K. If you play the ♦8 toward the ♦AJ, you get three diamond tricks. If you play the ♦Q, you get two diamond tricks. Playing low toward the ♣KQ98 will garner you two club tricks since the ♣A is on your right. That's a total of 12 tricks: three spades; four hearts, three diamonds, and two clubs.
North: ♠7 ♥K92 ♦AQ1085 ♣AQ75
South: ♠84 ♥Q107643 ♦K764 ♣5
This hand is an interesting one in terms of bidding. East opens 1♠ as Dealer. South will pass. West has five spades (♠AJ10xx), but only two doubletons and only six HCPs, so most people will bid only 2♠ rather than 4♠—no singleton, no void.
The spotlight turns to North. North would like either one more heart and one less diamond for a “perfect” take-out double; or one less heart and one more club to be able to bid 2NT—which would be unusual on this auction even though it is NOT a jump.
Life is imperfect. A double is the best bid. If partner bids a four card heart suit, at least you will be taking spade ruffs in the short-trump hand. Some Easts will pass, but many will bid 3♠, liking their ♣KJ108 of clubs behind the take-out doubler. Then South has the problem. I believe South is justified in bidding 4♥ whether East passes the double of 2♠ or bids 3♠. Here is the logic: you are allowed to assume a fit when partner makes a take-out double. With a fit, you convert to losing trick count. You have two spade losers; two heart losers; two diamond losers; and one club loser. 7 losers is an opening hand. Partner promised an opening hand. Bid game.
If E/W push to 4♠, North will double (having the minimum in terms of strength and in terms of heart length. N/S will get two diamonds, one heart, one club, and two club ruffs (with South leading his/her singleton club) If Declarer misguesses clubs, the defenders will get two club tricks. Down 3 doubled is most likely result.
If West jumps immediately to 4♠, now North has a headache. Some Norths will pass. Some will double. Some will bid 4NT (takeout—at least two places to play). Ironically, if North bids 4NT, South will bid 5♦ and they will make 5♦. If North doubles, South may bid 5♥—because the South hand has “negative” defense with so many hearts. Partner's likely ♥AK of hearts could be ruffed on this sequence and South “knows” from the auction that North has a singleton or void in spades. So, multiple contracts are possible.
There were a number of +150's N/S which could be 4♠ down three, undoubled, OR 4♦ by N/S, making five. There was one likely 5♦ making 5 (+400) and one 4♥ or 5♥ making 5 (+650) for N/S. One E/W pair was allowed to play (and make) 3♠, and two N/S pairs were minus in some unknown contracts. One E/W pair was doubled and went for 800, while another was doubled (in 6♠!) and went for 1100.