To answer this, I’ve deliberately not just gone and looked into your particular comment record to prime me with concrete knowledge. That way I can speak in broader generalities. Here are some common reasons why comments get deleted by a moderator:
- Comments that aren’t seeking clarification from the poster.
- Comments that have drifted off into discussions.
- Comments that no longer apply, like a question of the post owner which has been answered and incorporated into the post.
- Comments where people aren’t being nice.
- Comments that are actually answers and not comments at all.
- Comments that have any number of flags on them, from Not Constructive to Obsolete to Comment As Answer.
- Comments that just make jokes.
- Comments that just complain.
- Comments that contain inappropriately personal material.
- Comments addressing now-deleted comments.
Those are just off the top of my head, so please do not think any of those reasons are why yours in particular shall have gotten themselves deleted on you because of. They are not, save by coincidence. I haven’t looked at yours because I wanted to be able to write this answer without that bias coloring what I talked about here. Rather, these are all simply general reasons that apply to everyone, and I do not currently know which ones applied to yours.
Comments tend to be deleted by a moderator when they visit a post that has garnered flags. When there’s a flag on anything, we’ll normally also look at all posts not just the one that drew us there, so the question and all its answers as well.
If you spend time in the Low Quality Review Queue, you’ll have some insight into how often posts get kicked there, whether through a low quality flag or not-an-answer flag. These flags always gather like flies whenever one our site’s questions hits the Hot Network Questions list.
Additionally,the Community♦ Mod-Bot flags a huge whole lot of things, things moderators need to look at. Some of these are directly related to comment issues, but many are not. Still, it brings us.
And our users can and do — and should — use flags on comments themselves. Sometimes these are from the standard set, but we also get custom comment flags. Some of those custom comment flags’ wordings basically say “comment as answer”; I’ve seen a fair number of those sort over the past month. I have a suspicion that the evil single-word-requests and the even eviller hot-network-questions list may be driving those sort up.
I don’t usually overrule a comment flag, because most of them our members are right that there’s an issue with the comment or comments. Of course if they’re just flagging someone they disagree with out of spite, this is a different problem altogether and will be dealt with differently. But the vast, vast majority of comment flags are valid flags, or at least ones cast in good conscience.
There are only so many things one can do with comments. Sometimes we copy their discussions to a chat room, although that we can do once only. Sometimes we edit out the not-niceness if there’s salvageable content there. Sometimes we copy answers-as-comments into Community Wiki posts.
But if the answers-as-comments don’t make the least attempt at trying to meet our site standards for what we expect of answers, such comments will probably simply be deleted as noise. They aren’t actually helping anyone, and they run counter to the Stack Exchange founders’ goals for why SE should be useful and different from chat forums.
Comments can become a distraction, and wading through them doesn’t help anyone. They are meant to be things that can go without affecting the post. If they can’t, then they should be incorporated into the post or made into their own answers. That way their content can be indexed and linked, searched and found, curated and updated, and voted on by the community at large.
Those are really important features of SE.
Comments lie outside that system and those “features” of our community. Those capabilities are too integral to the SE experience to have ramifying content that exists apart from them. We need to be able to do those things with the content, and it is in no small measure because we cannot do those things with comments that they are held to be of no lasting consequence and value.
