While acting on what I understand to be normal/acceptable practice on Stack Exchange—that comments are disposable—I deleted about 180+ comments of mine on the “Science Fiction and Fantasy” site.
What I noticed is when I reached my supposed daily limit a red warning box came up clearly indicating I reached a limit (of 20 or so I believe?) and I could no longer delete comments that had at least 1 up vote to them… But I could still delete comments that had no up vote on them. Seemed like a bug, but regardless I went ahead and deleted more and more of my comments.
To be fully transparent, while it seems I clearly deleted more comments than are normally possible I at no point thought this was an issue as explained in this FAQ here:
Comments are disposable: unlike posts, there's no revision history, and they can be deleted without warning by their authors, by moderators, and in response to flags.
As well as here:
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. In reality, many obsolete or chatty comments remain untouched due to the high volume of comments posted, but this does not mean that they can't or shouldn't be deleted in the future.