I suppose it could not be retroactive, because in some cases it would no longer be possible (because that handle might have been taken in the meantime). So, those cases would cause problems.

So, I guess if someone forgets or fails to renew the domain, the previous default username will be used as the fallback, which is great.

How often does the system verify that the account owner is still the domain owner? I assume it is done periodically, but I wonder what the frequency is.

If I were a prolific poster, then probably yes. But only if the perks included a much higher character limit.

I like the CMS structure of Drupal very much. I like Twig, which I know from MetaBox in WP. But I hate wasting time trying to figure out, e.g. how to launch a Drupal multisite on some hosting plans. WP has a one-click multisite install, Drupal: facepalm. Such basic things must be simple.

Having to upgrade the core via composer sucks. As a "solo artist" it would be difficult for me to take a digital detox retreat, because Drupal might release a security update... I hope they will finally do automatic updates.

Yes, the recent behaviour of Matt Mullenweg is simply unacceptable.

I wonder what your plans for the future are...

I am looking at Drupal again, I had used it until 2013. It was cool, but the maintenance part was a nightmare. They finally have seen the light and want to simplify some stuff.