user24: When I edited What databases and listing sites exist for anime, manga, etc? yesterday, I also noticed that the comments there were quite out of date. They were suggesting changes that had already either been implemented or which weren't possible with the current SE markdown. There didn't seem to be any significant benefit to keeping them around, and the thread was pretty long and useless for almost everyone visiting the page. Hence, I deleted my comments, and flagged the one from someone else as obsolete.
I checked back today, and the flag was declined. I'm not sure why. If there was any lasting value in keeping them I could understand it, but as far as I can tell these comments are not useful to anyone and have not been for months (though they were when they were posted). Furthermore, with my responses deleted, the conversation is now broken so the discussion is not even readable anymore. Based on this MSO post, obsolete seems like a reasonable flag for this situation:

obsolete — for example, criticism of a post that has been satisfactorily addressed by the author

Why was this flag declined? Did the person responding to it see some value that I've missed in the comments here? Also, in the future, in cases like this where the request is to delete multiple comments on the same post, would it be better to use a custom flag?

user63: I declined this flag. I thought it would be better to leave the progression of comments intact in case other new users were to want to stumble upon this and had similar ideas (e.g. make it a graphic/spreadsheet/comparison chart).
Unless the comment stick out like a sore thumb, I personally believe it is up to the poster on whether or not their comment needs to be removed.
For future reference, if you want a string of comments deleted, please set a custom flag (or ask up in chat) with an explanation, this way it gives us a better context of the events that conspired.

24: <p>When I edited <a href="https://anime.stackexchange.com/questions/4696/what-databases-and-listing-sites-exist-for-anime-manga-etc">What databases and listing sites exist for anime, manga, etc?</a> yesterday, I also noticed that the comments there were quite out of date. They were suggesting changes that had already either been implemented or which weren't possible with the current SE markdown. There didn't seem to be any significant benefit to keeping them around, and the thread was pretty long and useless for almost everyone visiting the page. Hence, I deleted my comments, and flagged the one from someone else as obsolete.</p>

<p>I checked back today, and the flag was declined. I'm not sure why. If there was any lasting value in keeping them I could understand it, but as far as I can tell these comments are not useful to anyone and have not been for months (though they were when they were posted). Furthermore, with my responses deleted, the conversation is now broken so the discussion is not even readable anymore. Based on <a href="https://meta.stackexchange.com/questions/17364/how-do-comment-voting-and-flagging-work">this MSO post</a>, obsolete seems like a reasonable flag for this situation:</p>

<blockquote>
  <p><strong>obsolete</strong> — for example, criticism of a post that has been satisfactorily addressed by the author</p>
</blockquote>

<p>Why was this flag declined? Did the person responding to it see some value that I've missed in the comments here? Also, in the future, in cases like this where the request is to delete multiple comments on the same post, would it be better to use a custom flag?</p>
 63: <p>I declined this flag. I thought it would be better to leave the progression of comments intact in case other new users were to want to stumble upon this and had similar ideas (e.g. make it a graphic/spreadsheet/comparison chart).</p>

<p>Unless the comment stick out like a sore thumb, I personally believe it is up to the poster on whether or not their comment needs to be removed.</p>

<p>For future reference, if you want a string of comments deleted, please set a custom flag (or ask up in chat) with an explanation, this way it gives us a better context of the events that conspired.</p>
