<p>You ask about earning reputation for posting comments.  Because comments are "second-class citizens" on SE, they do not accrue reputation and you are not notified of votes on them.  The only thing they can actually do for you is earn you the <a href="https://stats.stackexchange.com/help/badges">Commentator Badge</a> and <a href="https://stats.stackexchange.com/help/badges/56/pundit">Pundit Badge</a>. By virtue of their absence, they can indirectly help others earn the <a href="https://stats.stackexchange.com/help/badges/40/tumbleweed">Tumbleweed badge</a>. </p>
