Um. So there is nothing wrong with it? It doesn’t look like fusarium or any other fungal disease to you?

Just weather damage....nothing to get concerned about. Might have the potential to develop into phyllosticta leaf spot however the control generally causes more harm than the leaf spot, which is only cosmetic, so spraying is not advised.

Agree with GG. And at this point in the year, my JMs still look ok. But by August/September some of them look like they've been blow-torched, a combination of wind and sun fatigue.

Won't hurt anything, but if you don't like the way it looks you can cut the leaves off in the middle of the stem (petiole) and a secondary leave will grow out.

Well as long as it doesn’t harm the trees health I won’t need to worry anymore. Although it didn’t flower this year

Not flowering is common with JM's. Some do, some don't, and some produce very few flowers. My 10 y.o. 'Villa Taranto' had one tiny little bunch of flowers this year, most of the others had none.

Not producing flowers as in it never will? Like a particular cultivar is programmed to never flower or it just takes a very long time for them to do so? My Mikawa yatsubusa is still under 3 ft tall but produces flowers each year.

Just that it is not necessarily a routine occurrence. As I stated, mine seldom flower but they are all container grown and healthy, happy plants otherwise. I don't consider it to be a drawback one way or the other

I don't grow JMs but I'm wondering if healthy, happy plants are less likely to flower in containers than stressed ones . What do you thing G.G?

I think that's a valid thought, floral, and one I had considered. But I just don't know. I come into contact with a lot of Japanese maples in the course of my business, virtually all of which are planted in the ground, and I have noticed the same thing. Some trees will flower and set seed with abandon and others, barely or not at all. So it's not just a container thing :-)

My limited research on the topic turned up no explanations. My comments are purely observational.