I wrote a comment to this question that helped user to find out why the error will be raised. The user answered with a comment and I get a notification. Now I cannot see my comment nor can I see his comment nor the notification. It is possible that he removed his comment but I think he cannot remove my comment. Few days ago I also didn't find a comment to an answer any more. But it could be that the poster has dropped the answer (including comments) and written a new similar answer. But that could not be possible for the post I mentioned above. Both comments contained hints to solve the problems and weren't rude or contained other problematic content. So there was no need for a moderator to remove the comments. How can comments disappear?
How can comments disappear?
From the main Stack Exchange FAQ section How do comments work?:
Comments are temporary "Post-It" notes left on a question or answer. You should not expect them to be around forever: Once a clarification has been made, an edit added to the post to include new information, or the issue in the comment is otherwise resolved, it is subject to deletion.
Also, from the comment everywhere privileges page:
When should I comment?
You should submit a comment if you want to:
- Request clarification from the author;
- Leave constructive criticism that guides the author in improving the post;
- Add relevant but minor or transient information to a post (e.g. a link to a related question, or an alert to the author that the question has been updated).
When shouldn't I comment?
Comments are not recommended for any of the following:
- Answering a question or providing an alternate solution to an existing answer; instead, post an actual answer (or edit to expand an existing one);
I removed those comments, as part of the routine clean up that keeps the focus on good questions and answers. Comments are not searchable, and add no long-term value to the site, especially for future visitors.
Once the answer by Balasz Papp had been added and accepted, the comments had served their purpose (though not a recommended one), and provided no additional information beyond that available in the accepted answer. Even if there had been something extra, adding a new answer or editing the existing one would have been the more appropriate vehicle.
Both comments contained hints to solve the problems and weren't rude or contained other problematic content. So there was no need for a moderator to remove the comments.
They weren't removed for rudeness or any other serious problem; they had simply outlived their usefulness (as explained above).
In fact, your comment was just as much a potential answer as the one that was ultimately posted as such, upvoted and accepted. The fact that it was routinely removed just reinforces the advice above: comments should not be used to provide an answer to the question.
Note that the text that appears when the 'add a comment' link is clicked says:
Use comments to ask for more information or suggest improvements.
I have un-deleted the comment in question for the time being to provide context for anyone that is interested.
Update: the comment has now been self-deleted and posted as an answer instead.
I agree with what Paul White said and I understand where you are coming from as well. In the short time that I've been here I've also noticed some of my comments being deleted. After I first noticed a comment was deleted I thought "WTF?" As I thought about it over the next couple of hours the more realized this is good housekeeping. Looking back at those questions/answers now they look cleaner, and I'm not tempted to expand comment chains to dig for more info.
Now when I notice my comments are obsolete I delete them and feel good about it.