@blabl Sorry for the late answer, didn't see this discussion at first. As
@stradrider pointed out, better start a new thread than post in an old one.
My question here is can there be a play let after the player score a point with the reason given as the opponent is not ready.
Yes, certainly! Although technically, there's no scoring of any points; the rally is a let as soon as the situation of a let occurs, even if the umpire takes a second or two to verbalize that.
In the example you mention here, the rally hasn't even started; the players have just hit a couple of shuttles. They are free to do that.
Can the player be allowed to challenge the umpire decision during tournament time if play let is called by the umpire with the reason the opponent is not ready although the player already scored a point?
No, there is no provisioning for the player to challenge
any umpire's decision except line calls. If the player thinks the umpire's understanding of the laws is wrong, they can appeal to the referee. Neither is the case here; both players started to hit shuttles before the match resumed.
Even his coach Keita Matsuda went to appeal to the tournament referee but to no avail.
It would be interesting to know the rationale for the appeal. Being a (presumably) professional coach, Keita Matsuda should know the rules, which clearly spell out in §17.6.8 that the referee can only be appealed to in questions of law. Which law did Matsuda think the umpire misunderstood?
So I will say that Li Shifeng win over Koki Watanabe is really invalid today because refereeing errors occurred many times throughout the tournaments.
I'm not sure how the tournament or even other tournaments are related, but let's assume that the umpire has made a grievous error, such as calling a receiver fault when there was none (or not calling a fault that happened), and is not corrected by the service judge (or referee if it was a matter of law, not perception). Then per §17.5 of the laws, the decision stands. Although a call would be faulty, the result of the match is still valid.
You will find similar rules in every sport: Incorrect calls should be avoided, but they are a part of sport. Even if you wanted to, it is not feasible to rectify an incorrect call by replaying a match. Umpires are neutral precisely so that any incorrect calls balance themselves out. And in badminton, one bad decision does not decide a match.
Somehow the incident disrupted Koki Watanabe all the way till the match is over.
Then he deserved to lose! The mental game is part of any tournament. There will always be something disrupting the player: Be it a draft, the playing time, the hotel, a fan, the noise, the light, a bad line call, an incorrect call, or even – as here – a correct call! A true champion perseveres, and mentally switches to the next rally.
Often time I find umpires wrong decision during tournament time as baffling
There's a simple remedy for that: Become an umpire yourself! The first umpiring grade is usually achievable with a weekend or two of training, and should be basically free. Learning the rules in detail will empower you to distinguish surprising but correct calls from umpire errors. And umpiring yourself will give you a better feeling of why an umpire may make a mistake.
