Given some of our recent discussions on meta, it seems the community is particularly sensitive to moderator deleting comments that are related to moderator behaviour. This question has a "not constructive" flag raised against one of the comments, which has brought it to my attention. It seems to me that all the comments form a discussion that is not relevant to the question, but may be the basis of a useful chat/meta discussion, unfortunately the only options available to moderators is to leave the comments or delete the comments. Should the comments be deleted?
These without a doubt meet the criteria for deleting comments:
they offer nothing of value to either the author of the post or to future readers.
These are meta-comments about the potential closure of the question. The only vote to close the question has long since aged away. There is no ongoing debate over closing the question (and the question never even came close to bring closed, by moderators or anyone else). The entire conversation is almost two years old. The person who posted those comments was invited to bring the concerns to meta, and declined to do so.
Given the current vote counts on this question which was about a much more borderline case, I don't think there's any reason to believe that the community majority would want to keep those comments around.
Here is a second shot at posting what really is an answer to the question. That answer had a feature which proved to be distracting and controversial, so I am trying again without it.
Moving comments to meta is much less potentially objectionable than deleting them outright. It would be easy enough to keep one or more meta questions open for the purpose of transferring comments that pertain to moderation (and/or other meta issues).
The point of the meta site is to provide a platform for discussions of site mechanics. It is natural that many discussions of site issue begin on the site itself, and I don't like to see discussions which begin there deleted outright. However, "I have moved this discussion of site issues to the dedicated place for site issues" ought not to be problematic to anyone.
Note also that moving such discussions seems easier and faster than wondering whether or not to delete them and especially to having discussions about the suitability of deleting questions.
I do not myself see much of value in the present comments, and deleting comments that are more than a year old and have not been acted upon is not a problem to me. But I think that the general practice of moving comments to meta rather than (or technically speaking, along with) deleting them is a good one. I hope it does not take much more work for moderators to do this. If it does, a streamlined way to move comments to the meta site seems like a eminently reasonable feature request.