I learn more about sente and gote
Back to ancient times.
I originally learned about sente from the English version of Korschelt, about the value of taking sente instead of following your opponent around and of keeping sente when possible. I also learned about sente plays, which threaten the opponent with severe loss (according to Korschelt). Later, as an SDK, I learned about the classification of plays as gote, sente, reverse sente, and double sente. I also learned the rule about doubling the swing value of sente, without explanation. I also learned about assuming that sente are played when estimating territory, and the saying that sente gains nothing. (The two go together, and I understood that. If sente gained something, then it would not make sense to assume that sente are played when estimating territory, as that would change the estimate.)
As I said, I began to have doubts about double sente, in particular the double kosumi on the second line. I saw one pro game where it was played in gote, and after that I noticed that pros often left it on the board for some time without playing it, a violation of the saying to hurry to play double sente.
As I also mentioned, on my own I developed a probabilistic understanding of gote and sente, at least in evaluating positions and plays. Since we assume that sente are played, the probability of playing a sente is 100%, and the probability of playing a gote is 50%. That gave me the correct values. I did not think about it, but that did not allow for evaluating double sente, as it implied that each player would get to play the double sente.
I finally understood the rule about doubling the value of sente, when I read somewhere about evaluating a simple ko at 2/3 of its swing value. The point was how much each move gained. There is one move difference in a sente, two moves difference in a gote, and three moves difference in a simple ko. You double the swing value of sente instead of taking one half the swing value of gote because people find it easier to multiply by two than to divide by two.
I did not think of the implication for double sente, dividing by zero.
I had also forgotten Korschelt’s idea of sente as threatening a severe loss. I told beginners that a play was sente if it carried a threat that was larger than anything else on the board. Not exactly accurate, but close enough.
But I was still operating by the seat of my pants. Often whether a play was sente or gote was obvious, but not always. And what about plays that were sente, but did not carry a threat that was larger than anything else on the board? Obviously they could not be played with sente yet, but presumably they would eventually, with very high probability.
Normally, as the ambient temperature dropped (as we now say), there would come a time when the largest play elsewhere would be smaller than the threat of the sente but larger than the reverse sente. At that point the sente could be played with sente. There might be exceptions, but that was the general rule. So we started with the idea that a play is sente if it carries a threat larger than the largest play elsewhere on the board, and we get a new idea that a play is sente if it carries a threat that is larger than the reverse sente. Eureka!
Later that got refined to the idea that a play is sente if it raises the local temperature and initiates a sequence of play that drops below the local temperature with a play by the opponent.
does not qualify as a sente because it is a gote. It gains 5 points and then 
gains 4 points in reply, so that the sente sequence gains 1 point. I agree that the proverb is somewhat confusing, especially as traditionally plays are classified as double sente, which may gain something.
the count is still 0. White has a 1 point sente left at 3, which results in a local net score of 0.