I don't really see the purpose of this feature. If a post is worth engaging with then that should be the case whomever it comes from, and similarly if it is not. Providing users with tools to more effectively "pre-judge" what others have written seems likely to foreclose opportunities for discussion and mutual understanding. People can surprise you.
I can see the suggested feature being useful for moderators to keep an eye on new posters, but for regular users it seems somewhere between superfluous and actively harmful. If one believes that certain posters consistently bring nothing of value to discussions, there is always the block feature, and of course the report button if the content is actionable. I'm not sure if there is a "follow user" feature to keep track of folks who consistently post interesting, informed, or thoughtful material, but I could see that being useful.