I don’t think there is “the compelling” reason of not breaking code and that “only mentioning confusing by beginners” is an only. It’s a good reason. We should strive to keep the language simple, and I don’t see a huge benefit in expressivity having this quite marginal feature. AFAIK post-fix syntax makes parsing code harder, and I think it also lacks regularity; for example, can you use post-fix syntax with types like List String?
Before arguing that it will break people’s code, one would have to present some statistics of how widely it is used. My guess is that the number of uses are neglible, and where it is used, authors wouldn’t have a strong stylistic opinion on it.
Does Dotty support post-fix syntax?
best, .h.h.