using the two classes will create confusion and not provide the backwards compatibility you expect. The pipe character does not do anything. Both classes are applied

I know both classes are applied. That is the purpose. The pipe is there only to separate the new classes from the old ones (or deprecated) without the need of a documentation. The point is for developers to know the meaning of the pipe and to start using the classes before the pipe and ignore the classes after it. Adding many classes does not mean that all will apply a style to the element. The template will decide which one will use. Of course, at the beginning, the already created templates (like Cassiopeia) will keep using the classes after the pipe but as they update they will use the classes before the pipe.

Why would they even bother. Seems to me that the only reason for this change is to satisfy your own personal design ideas and as had been said by many people before - that is why we have template overrides.

Actually, the changes I suggest are not only different class names. There are many cases where classes do not exist at all, or even more, there are no tags for adding the class. For example, in the info block, there are parts that need special css tricks in order to modify. I guess your answer will be still the same: "override the template", but I keep facing these disadvantages so often and I don't feel good to see the new Joomla 4 to continue having these disadvantages. It is like having a Ferrari engine inside a white old car of 80s. Furthermore, the overrides are good for special needs and not for everyday styling and also for not so many files.

All I want is to propose something that I consider good for Joomla. If the rest Joomlers don't agree, then at least I will have tried for what I believe is better for Joomla.

I dont understand why you dont want to use the tools provided - template overrides?
Nor do I see any advantages of these changes? The only changes proposed here are renaming

What I understand from your side is that you don't want some random strangers (like me) to suggest crazy ideas and ruin Joomla. I agree with that. But on the other hand, who would come here to use this Github thing and mess with the code of many files and spend time if at least it was not for serious reason?

But you dont explain the reasons

Here are some reasons:

1. Joomla 4 is a general improvement of Joomla 3. Why an improvement to the HTML code (including some bad class names, some missing classes and some missing tags) not to be included in this improvement?
2. When I create a simple website that doesn't need overriding but simple CSS styling, I don't want to see these inconsistent classes like: com-content-article__body, page-header, item-image, article-info... Sometimes it is article, sometimes it is page, sometimes it is item!
3. I believe that overrides are for special and hard cases and I have done overrides many times with great result and satisfaction. But I don't want to create permanent overrides on maybe 15 files just for using them in a simple website. I would like the new version of Joomla to provide the basic needs.
4. Finally, how can I be sure that during all these years of Joomla 4 life, there will be no code change/upgrade to all these overridden files? I want the override to be an exception, so the other files to keep upgrading.