Thanks for those good wishes, Mare.
I'm no techie, but I can't see how a few initial public posts (which could easily be bland and innocent-looking dummies generated by a computer) will prevent determined bad guys building the launch pad for a mega-spam attack once the PM system has been enabled for their account.
If the site owners are really relying on that, we are all being defended from the tide by castle walls built of sand. Surely their coders have constructed more effective barriers. If so, why hassle people with such irritants as an unannounced ban on starters' PMs? And if not, horrors! They need better consultants, who won't try to treat gangrene with itchy sticking plaster ...