Surprising we don't have that yet.
If we add this - which sounds like a great idea - there should be a landing page for the newcomers saying something like this:
Hey, look, nobody likes spammers, so we added a waiting period. You can still browse, just not post or comment for this long. After that, you're welcome to introduce yourself to the hubskifolk! Just use #newtohubski as one of your tags!