I think that'd kinda suck. posting is the only act which could be called "participating in the community" here. If you restrict that, especially to a small number, you prevent people from participating when they want to.
Besides, it's not that hard to skip over or skim over "the same new people"'s posts and just read the ones you're interested in. If someone's really getting off topic or saying something really offensive, you can always use the "report this to a moderator" tool, as well.