Comment spamming is a general practice today, some webmasters post irrelevant comments on others blog to just increase their site ranking in SERPs. But now it will be damaging to both; the website whose link is post in comment and blogs/website which allow these types of comments. Detailed information is given in a recent Google Webmaster Blog post about comment spamming.
Webmasters should do following things to maintain their site ranking
Don’t post irrelevant comments just to get a link.
Comment only when you think it can provide more information on particular topic
Comment when you want to start a new discussion
Till now if you were practicing comment spamming to increase your website ranking, you should stop immediately otherwise it will now work in reverse direction i.e. lowering down your website/blog ranking. Now start working on finding the new ways to improve the site ranking, otherwise you may find yourself in problem.
Bloggers should do following things to maintain their site ranking
Don’t allow spammy comments on your blog
Delete all the spam looking comments from your blog
Use anti spamming plug-in in your blog
Don’t allow anonymous comment posting
Prevent automated spammy comments
Always use the comment moderation option
Use “nofollow” on comments
As a blogger if you don’t consider above factors then one day you may found that in spite of all your hard work your blog rank is going down because somebody else is trying to increase his/ her blog/website ranking through comment spamming. Don’t let spammers ruin your good work.