Call me old fashioned, but I'm okay with an upfront waiting period. Back in the day, when the sun was brighter, dogs behaved, children didn't sass, and milk was delivered to your doorstep before the kettle boiled, it was normal to wait x days or x comments in public subforums (whichever came second) before you could post or access a full forum. It used to be okay to expect people to wait before letting them in.
I assumed the trend towards instant gratification and full participation rights was driven by desparation to bolster the size of a subject population. Um. I reread that and I'm appalled with myself. I don't have time to rewrite it (family beckons, dinner time), so I'm claiming it as deliberate art.
Whatever. Having an 'ignore noobs' option might preserve the illusion of welcome for newcomers while protecting alumni from "HHHAH D1XBUTTER CHECK IT" or 7 reposts of an excerpt from a 2 month old New Scientist. But an internet-savvy and genuine new user who contributes from Day 1 might be discouraged if no one sensible acknowledges their contribution.