<blockquote>
  <p>Aren't we supposed to flag obsolete comments?</p>
</blockquote>

<p>Yes, we are; but how the flag will be evaluated is subjective and it depends on many things, one of them is the Stack Exchange community.</p>

<p>For example, here I have flagged 32 comments and have collected 13 declines (which is pretty high ratio; 40%), while in Stack Overflow I have flagged 54 comments with just one rejection). On the other hand, when it comes to flagging posts, I am not so bad on both sites: 39 declines out of 572 (7%) in CV and 21/1285 (2%) in SO.</p>

<p>Deleting comments is a tough action, because it demands time reading the whole context, it is not a priority (except for offensive comments), and there is always the risk someone will complain and demand more time from mods explaining their actions here in Meta, chat, etc. Some mods are more conservative deleting comments than others.</p>

<p>So the best thing to make is to feel how flagging comments goes in the community you are, and take your chances of flagging according with it. I used to flag more comments; now I only do in very obvious cases (this is not a complaint).</p>
