Out of curiosity, I was looking up the rules of kendo, and a very peculiar rule stood out to me. If a player celebrates in any way after winning a point, even with a subtle fist pump, the point can be nullified/taken away. Personally, this sounds utterly baffling. Apparently, it is seen as disrespectful to the opponent to celebrate a point in kendo. But how, and why? Why is it disrespectful in kendo, but not in other sports?
The main sport that I follow is tennis, but I'm also familiar with rules of several other sports, and none of them have such a rule. In fact, celebrating a point to increase one's morale is encouraged in many sports. But I'll use tennis as my main point of comparison since it's what I know best.
For example, in the 2019 US Open Rafael, Nadal scored a point against Cilic by hitting the ball around the net and into the other court. He then lets out a loud yell, and understandably so. The shot that Cilic hit was extremely difficult to return, and hitting around the net is extremely rare and very difficult to do. It seems fitting to celebrate after scoring such an impossible point. https://www.youtube.com/watch?v=fBw63IFYaRk
Don't get me wrong, tennis also has many stringent rules and regulations, and sportsmanship/respect is highly valued. Tennis has a reputation for being a snobby/uptight sport because of that, but even then, celebrating a victory is seen as a normal thing to do. Seeing the emotions of the players displayed on the court is part of the experience.