Most blog owners and blog commenters are probably entirely unaware that the links left in a commenter’s signature do nothing to increase PR (page rank) of the site to which they point.
I discovered this when I stumbled across an article entitled PopulaR in Turkey? on the Vanilla Mist blog. This blog has a very high PR, and attracted a lot of spam comments as a result. But as explained in this article, the spam does not help the spammers at all!
On many blog systems, you can leave a comment with your name and your site’s URL. When published, your name becomes a hyperlink that points to your site. This brings traffic to your site if readers click on your name.
Most people assume that this link also boosts the page rank of their site. However, in most cases it does not. This is because most blog systems (WordPress, Movable Type, Blogger etc.) attach an attribute to the like called nofollow. When search engines crawl the site, they do not count links tagged as nofollow towards PR.
This has several effects. The most immediate effect is that comment spam does not pollute search results.
If you are trying to leave helpful comments and at the same time boost the PR of your site, you will not get a direct boost in your PR at all.
trackbacks have a similar effect. If pings are enabled on the target blog, an article like this one (with a reference to a specific blog article) will earn a reference back to it, much like a comment. Again, these references almost always have a nofollow tag. But they are still worth doing if legitimate. Don’t waste your time though, if you are doing it just to boost PR of your site.
So should you stop commenting? Well, yes and no.
I must say, that at first read about nofollow, I was a bit miffed that commenters are not rewarded for commenting. But then when I thought about it, it I realized that it is the author who should be rewarded for writing a good post by getting comments!
By participate in the online community with helpful comments, you are making a contribution. That may attract people to your site, and if they like what they read on your site, they might refer to it on theirs. If the blog writer has a link to your site in the blogroll or in an article, that counts towards your PR.
So you need to write helpful comments, and you need to produce a website with good, well-written, original content. Commenting will eventually lead to good PR, but indirectly. Electronic karma at its best perhaps.
If more people are aware of this, the result of the rel=nofollow attribute should be to reduce comment spam and comment noise, and increase the quality of writing on the web, or at least push the quality writing towards the top of search results.
PS your comments are most welcome as always!
PPS I have changed my mind about much of what I have said in this article.
For an update, read: