I was asked this question at a game today:

Initial reaction is 'No', because it is natural, but then it does have a specific meaning in many, if not most, systems.

???

• I think it would be alertale if it has an unexpected meaning or value

something like:

1D - 1S
2H?

If 16+ points, 3+ hearts (normally 4+) and forcing for at least 1 round, then this would be natural, expected and not alertable.

If this shows 10-15 point and non-forcing, then this would be unusual and alertable.

If the 2H bid shows shows specific holdings (such as guarantees the A or KQ minimum in H) then I think that this should be alertable as this would at least be important in defence.

• @Martin said:
I think it would be alertale if it has an unexpected meaning or value

something like:

1D - 1S
2H?

If this shows 10-15 point and non-forcing, then this would be unusual and alertable.

It's not practicable to make it alertable, because players who play reverses as non-forcing rarely understand why it's not normal.

• I was meaning if they, by agreement, make this weak... rather than poor/inexperienced players not alerting because neither knew that this was a reverse

As a similar principle, with my main partner we have an interesting bid where a jump shift into a higher ranking suite was weak with a 6 card suit, such as 1C - 2H = 6-9 points, 6+ Hearts including an Ogust continuation if needed.

A jump shift in a lower ranking suit is 0-5 points with 6+ cards (normally 7) with no tolerance for openers suit. For example, 1S - 3D = 0-5 points.

While both are natural bids, they by agreement have an unusual value meaning, we alert.

Same principle with a reverse, if by agreement this is non-forcing and weaker than the expected range, then it should be alerted.

• Provided it does not have a potentially unexpected meaning, then it would not be alertable. Law 40B5a

1. (a) When explaining the significance of partner’s call or play in reply to an opponent’s
enquiry (see Law 20) a player shall disclose all special information conveyed to him
through partnership agreement or partnership experience but he need not disclose
inferences drawn from his knowledge and experience of matters [b]generally known to
bridge players[/b].

White book 1.3.1
...
General bridge inferences, like those a new partner could make when there had been no discussion beforehand, are not alertable.
...

Since there is no need to disclose such an inference then an alert is not needed.

Alert (def) : A notification, whose form may be specified by the Regulating
Authority, to the effect that opponents may be in need of an explanation.

I would say that an alert would only be needed if the reverse could be made on a hand which could have a distribution different from that usually expected (4=5, 4=6 etc) or one that is weaker than usually expected (by partnership agreement of course).

• I think a reverse can only be alertable if it means something unexpected. An expected meaning would be something like "the second suit is not longer than the first" (unless the first suit was alerted as canapé, in which case the second suit is not shorter than the first), and "the bid does not deny a strong hand". (Either using the bid to show strength, or to show a distribution that would require the suits to be bid in the given order, is reasonable/common for a reverse. Of course, many (most?) bridge players use a reverse to show both at the same time!)

Martin wrote:

As a similar principle, with my main partner we have an interesting bid where a jump shift into a higher ranking suite was weak with a 6 card suit, such as 1C - 2H = 6-9 points, 6+ Hearts including an Ogust continuation if needed.

I'm actually interested in whether this "should" be alertable or not. There are at least three common meanings for a jump shift (very strong; weak with a long suit; constructive with both the opener's suit and the suit jumped into). I wouldn't consider any of those meanings surprising. (Most bridge beginners are taught the first, but it comes up so rarely that a jump shift observed at the table is likely to mean something else!)

• I think that 1H - 3C would be unexpected to show 0-5 points?
Also, at least at the clubs I play, 1H - 2S - 0-6 point would be unexpected

• Weak jump shifts are alertable.

4 H 2 Because they have a potentially unexpected meaning, players must alert:
...
(d) A non-forcing new suit response, to a non-forcing suit opening at any level, below game, unless responder has previously passed, bids over a natural NT overcall, or makes a double jump

• BB 4B1:
A bid is alerted if it
"(a) is not natural; or
(b) is natural but has a potentially unexpected meaning."

BB 4C1:
Amongst the things that are considered natural for alerting purposes are:
"(a) A bid of a suit which shows that suit (4+ cards for an opening bid of 1 or higher or any
overcall, otherwise 3+ cards) and does not show any other suit; preference bids,
completion of transfer bids and raises may be on shorter suits."

If a reverse is played in the traditional manner (first suit longer than second; extra values), there is nothing that is not natural; and nothing that is unexpected, so no reason for any alert.

Other possible agreements involving reverses include:

A: If you play 2/1 GF, there is no longer any logic that dictates that a reverse after a 2/1 response should show extra values. People play it both ways. As a player if I played that opener could reverse with minimum opening values, I would alert because opponents might not expect it. As a TD, however, I would be dubious about the question of damage if there were no alert.

B: If you play 5-card majors, there is a structural issue if you open 1 with 4-4-4-1 distribution and partner is foolish enough to respond 2. If you play that a reverse shows the traditional extra values with a longer first suit, to do that, particularly with a minimum, would be a distortion, so you have to find some structure to cope. There are three obvious options:

(i) The French just rebid 2 , which specifically does not guarantee more than four diamonds; 2M shows a traditional reverse (4M + 5 , extras).

(ii) It is perfectly playable, as long as the 2/1 promises a rebid, to play that all hands with 5+ diamonds rebid 2 , which neither confirms nor denies a major, and neither confirms nor denies extras. The 4-4-4-1 hand "reverses" into hearts (or perhaps spades if the spades are very strong and the hearts very weak). This specifically denies more than 4 diamonds, but neither confirms nor denies extras.

(iii) Avoid the problem by opening 1NT if in range and rebidding 2NT if out of range.

Which of these possible rebids do you think should be alerted? FWIW, my answers would be:

(i) Alert 2 (the rebid of a potentially 4-card suit being unexpected); do not alert 2M
(ii) Alert 2M (the fact that there may only be 4 diamonds and the fact that there may not be extra values both being unexpected). I would incline to alerting 2 as well, although the Walsh analogy* suggests otherwise.
(iii) Announce the 1NT opening; No alerts for 2 or 2M rebids, as they show minimum with extra length and a "normal" reverse, respectively. I wouldn't alert 2NT just because it could have a singleton in partner's suit.

*Walsh-style responses to a suspect 1 bypass equal or longer diamonds to bid a 4-card major unless the hand has a defined level of extras. I believe that it is established in this scenario that the 1M response is alertable but the 1 response is not.