What is the criteria for deleting comments? Why isn't there a notification that a comment was deleted? Just today, I gave a big thank you to a contributor (Ed Beal) whom I respect a lot for supporting my answer, calling it 100% code compliant. Then when I looked again at my post my thank you comment was GONE! I realize the actual questions and answers have a more strict protocol, but I thought comments would be more casual and not subject nearly as much scrutiny. Certainly not to the extent of deleting them with no notice or explanation... this needs to change. BTW, it was on the DIY portion of SE.
When adding a comment, there's a visible placeholder text:
And in words:
Use comments to ask for clarification or add more information.
It's there for a reason, to explain what you should write as a comment. Anything else would be candidate for deletion, without any notice.
Back to your case: a comment to thank someone, no matter who it is or what they did, is not asking for clarification and it does not adding any information. Hence, it's expected such comments would be deleted.
I believe your core problem is confusing Stack Exchange with social networks, where comments are important part, perhaps the most important part, of the network. Stack Exchange is platform for Questions and Answers, where the focus is the content, not the people and neither the comments made on the content.
Also, note there's whole faq for how to properly thank people who posted content you find useful: Thanking users who answered my question
One common criteria for flagging a comment for deletion is:
- It's no longer needed.
This comment is outdated, conversational or not relevant to this post.
This is because long strings of conversation, or comments like "Thanks a bunch!" are rarely useful to other people reading the post later down the line.
Presumably the comment was flagged as such and consequently deleted (possibly by the person you were thanking, after they read it). In your particular case deleting this comment perhaps seems a bit harsh.
And I agree that a notification for when a comment is deleted would be nice, but I don't think it's necessary.