This is welcome news.
Previously, if your username was reported to Sony and deemed offensive, your account could be outright banned and your appeals might even fail to achieve anything.
Since usernames couldn’t be changed, there didn’t seem to be any compromise.
Saved game progress, trophies, digital content - all gone.
So, I am glad to hear that Sony will now be changing your username in such a scenario to a temporary one, which you can then change again to something preferable.
This, as I understand, is the Microsoft/Xbox route and I would say it’s much better than the previous Sony/PSN process.