Anyone can create a low quality posts, making HQ posts isn't based on the user rank, though i know there are more high ranked users making quality posts and those that do not are in the minority, but that doesn't mean you would categorize all high ranked users as quality posters, or insinuate they bought their accounts cause of the qualiity of their posts. Mind you also that not every user started from scratch, some were airdropped merits and they have not earned a lot since then, but they still have a high rank as a result of the merits they received via airdrop.
The fact people sell or buy accounts shouldn't discourage users who do not, and who are willing to continue learning and growing the normal way. And No, buying/selling accounts isn't a bannable offence.