I have a blog installed on my site, many people are posting comment on my post
I have checked these comments are already available on many sites, people are posting same comments on many sites
I want to know these comment worth for my site or I have to delete it
Spam comments is one of the thing you will have to deal with as a blog owner. It is a problem that most people know too well about. Like @webspider said above, leaving those comments make your site look popular. You might consider making your comment available only to those who sign in.
I take out comments without any relevance to my post whatsoever. They just look like clutter. I keep those that are sensible, regardless of whether they are just dropping links. I have no problem making my blog dofollow, because I know how it is to be at their position. I have done the same thing, too. So nothing wrong with helping one another
And hey, there really are people paid to comment on blogs and drop links but really read them and learn a thing or two. So if my primary purpose of keeping a blog is to inform and educate people, then I don’t think comments with links does not in any way interfere with this objective.
Everyone try to get backlinks in many ways and in my view blog commenting now a days everyone keep on posting something and give a url thinking they would get a backlink. But it does help only at few point. If the post is really valid you can add it no matter what ? give the link as no-follow. But if it is some kind of promotion then just spam it.
Good strategy is to have all your comments as dofollow link - that way you will attract whole bunch of visitors (people trying to leave backlink on comments), plus your blog will be linked from other blogs in those “dofollow blog lists”.
But dont forget to use moderation approval, and let go only comments that you consider to be valuable add to your blog post.
Spammy comment may be too much back links with keywords you may modify them but should not delete them because more and more comments on your blog posts make them popular on search engines and that thing will helps to improve blog popularity and search engines likes those kind of blogs and SE’s automatically promote them.
If the comments are valid and good then keep them. Multiple dupicate comments from the same person do not make your blog look good and if anything badly moderated. If unsure abotu a comment just remove it - better that way.
Our blog gets comments that are outright spam and then those that can be considered borderline. The borderline ones often talk about something in the article. For example, they might say “Great point” and mention why they agree or provide their own suggestions. However, those close out the comment with their name and a link to their blog or site.
These I usually leave up because while they are link dropping, they also took to the time to actually skim the blog post and leave a somewhat relevant comment.
Anything else I delete though and while having a lot of comments on your blog will make it appear popular, I won’t personally want it overrun with spam.