Earlier, on the blog, it was mentioned that we are not completely free to choose the URL structure, because some plug-ins require a specific URL structure.
However, I just tested changing the URL structure to /123/why-do-birds-not-sing (the simplest one), and it seemed to work. I tested every single of the plugins in every possible way, and it worked always.
Why, then, are we using the most complicated, quite-difficult-to-memorise URL structure /index.php?qa=123&qa_1=why-do-birds-not-sing ?