If the comments are genuinely not relevant to the post they are attached to, the best thing you can do is probably to flag them, or the post itself, for moderator attention to draw attention to that fact.
When flagging, please make sure to use a descriptive flag reason. A bunch of comments simply flagged "no longer needed" can be difficult to handle because it provides no information on why the comments would be "no longer needed", but a bunch of comments flagged "no longer needed" plus one comment flagged "this and others completely unrelated to the post" is much more descriptive. Flag reasons are limited in length, so don't worry about leaving out an unnecessary word or two; just make sure the intent is clear.
Moving comments to chat is more likely to be done with ongoing discussions, whereas the specific case you refer to seems to (with the exception of one comment from this January) have been active most recently in November 2015. Generally, I'd say that there's little value in keeping "useless" comments that are over two years old. In fact, I'd argue that broadly speaking, there's little value in keeping any comment that is over two years old.
In the words of Monica Cellio:
moderators get an auto-flag if a post gets 20 comments within three days, but that velocity is very uncommon here. When in doubt, flag.
Remember: Comments are intended as ephemeral "post-it notes". If there's something in it that's actually worth keeping, it should probably be incorporated somehow into the post that the comment is attached to. Comments can be deleted at almost any time for almost any reason, including (but certainly not limited to) that a moderator happens to come across the post in normal browsing of the site and seeing a bunch of old comments that appear to have been incorporated into the question or any of its answers.
In this specific case, I've purged all comments on the post except the one from this January which does appear to add a useful anecdote, though ideally that one should be captured elsewhere, possibly as a question and answer on how to handle the issue of publishing under a pseudonym as an author publishing via Apple iBooksStore.
There's no reason why we couldn't move comments to chat, but comments that get moved to chat should ideally be somehow useful, or the people involved should be actively engaged in discussion. The system will also automatically offer to migrate comments to chat if a few people engage in repeated back-and-forth in comments; I'm not sure what the exact triggers are, but in my experience it has generally been fairly accurate in making such suggestions.