Comment on SEO Super Comments WordPress Plugin by SEO Dave.
For comments that lack a title add one as soon as possible.
For not so good comment titles, depends how bad the title is, if really bad edit it ASAP.
The rest check them on a regular basis and modify to support your sites SERPs.
It’s about giving the comments context and gaining SEO benefit. If you have a lot of not so good titles they are highly unlikely to rank for anything in Google and so less traffic and don’t add SEO benefit to the main article.
Don’t be concerned about using the same comment title multiple times, even though ideally all comment titles would be unique it’s not easy creating a unique title for 50+ comments on a post (on this site I manually edited all 3,000+ comment titles including using keyword research to know what to target).
The comment title used for this comment (Comment titles) has probably been used for other comments on the article about comment titles. The anchor text will help this post because it includes one of the main keywords “comment”.