Why is separating class ind struct is bad?

[Danni Coy via Digitalmars-d]

> Could anybody explain what this mean and why this way is not modern?

This is in the context of users migrating from C++, and it is bad in
so far as it is not what a C++ programmer who hasn't read all the
documentation would expect.

The easiest path of migration would be if the programmer can design a
program the same way they would a C++ program but using D syntax.
this, transitive const and I think thread local by default make
migration in this way harder. (Though probably worth it in the long
run)