Some time ago I promised to write about my approach to use of nofollow for blog comments. Personally I do think that all comment links at dofollow blogs have no SEO value, and now I’m gonna clarify my thesis.
Being out of the “context”
If you are interested in SEO, you know well that links from sites topically related to yours can offer measurable boost for your rankings. So if you do SEO for a website about gaming, in most cases links from sites run by people interested in gaming do best for your business. Unfortunately, that thing is also able to work in a opposite way - if all of links to your site are coming from bad neighborhoods, your site probably will be not marked as a trustworthy place in the web, too.
Number of external links on a single page
There are two different schools of SEO, one claims that number of outgoing links decreases your Google PageRank. In my humble opinion it’s enough to know which of them is preferred by services owned by Google - both Blogger and YouTube do use nofollow for all needless external links. Consider it.
Even short comments matter
My friend from Italy made a smart WordPress plugin that does block all short comments before processing. However, I’m afraid this is not the best way to fight spam. Even a few-word-long comment could be fine, don’t you think so? Just take a look at comments at Digg, or Reddit.
There’s only one good way to share the link juice
When you remove “nofollow” from comments written on your blog, your link juice simply gets out of your control. And I think we can say that use of dofollow plugins can only decrease both PageRank & TrustRank of your site. Sharing link love with people that participate in local community by making use of Top Commentators ranking looks much safer to me. When someone does have a “spammy habit” you can easily add his name to the blacklist. Don’t you agree with me, Erwin? 
September 19th, 2007 #
Indeed, I believe that we need to learn from Blogspot, since it’s owned by Google.
Giving dofollow for comment links makes commenting valuable, visitors gain SEO_Power. So you get more comments. If you have “top commentators” installed, you give SEO_Power only for few people, so it’s something like you had contest for “who writes most comments”. So you probably get even more comments.
September 19th, 2007 #
Krzysztof: What are you thinking about? Which option is better: to save SEO power for sites linked within your posts & Top Commentators ranking, or to have a spammy-stinking blog-bucket? I don’t have a dilemma, guess you do the same.
However, larger amount of comments is pretty delusive haha
September 19th, 2007 #
Every young blogmaster (blog owner) wants to have as many comments as possible. The younger he (she) is, the more intense is that urge.
I simply want to have comments so I know that my work is being read by others. I also want to know if they think what I write is interesting and what they me to write, ’cause sometimes I know I should write something but don’t know what…
September 20th, 2007 #
It’s all about Hitnosis (refreshing your browser repeatedly to see if your hit counter or comments have increased), Commentariat (readers who comment) and Blogstipation (writer’s block for bloggers).
September 20th, 2007 #
I only have RSS readers counter, and watch hits on Analytics with one day delay. Good for me.
September 22nd, 2007 #
[...] by search engines. Google’s Webmaster Guidelines says “avoid links to web spammers or bad neighborhoods on the web, as your own ranking may be affected adversely by those links“. Just guess what if [...]
September 24th, 2007 #
I personally haven’t got a problem with dofollow or top commenters. It really should’t be an issue. We’re only discussing it here because it gets abused. If someone wants to use nofollow then thats fine - people shouldn’t be leaving comments just for the link.
September 25th, 2007 #
[...] I can plead guilty - call me a freak just as you like. But you better move on and check your sites with this tool OR you won’t [...]
September 26th, 2007 #
Wikipedia has flip flopped with this but I believe currently they are using nofollow.
September 27th, 2007 #
And this is exactly why I do add rel=”nofollow” to every link to Wikipedia
September 27th, 2007 #
Me too.
If they don’t share their PR, I won’t be giving them mine either…
September 27th, 2007 #
nofollow is a complete fallacy… if you dont want outbound links form your comments dont give people the option to post url’s simple as that. the principle of nofollow is complete lunacy. “add your link… but ah HA… we’re not gonna give it any weight” whats the point.
September 27th, 2007 #
And I always thought that leaving comment with url gives me some visits from people interested in what I have to say.
September 27th, 2007 #
As well as nofollow added to links doesn’t make spammers much impressed
September 28th, 2007 #
@ Mark Rushworth - I must respectfully disagree with your statement, because there is still a value to putting your link in a comment even if it is nofollow. That value is that it’s still a gateway to your site, even if search engine spiders don’t follow it, users like you and I can. I often see commenter’s links getting clicked hundreds of times on my site if they make a good comment.
@ Krzysztof Lis - You’re exactly right, it does. I’ve clicked on all of your (Bart’s commenters) pages before.
September 28th, 2007 #
Jon Holato: yes but as far as SEO goes, only on Yahoo and to a lesser extent MSN. Any click based traffic is purely based on comment merit and as we’re not selling anything through comments the chances of a conversion are low.
September 28th, 2007 #
I found a good explanation of it - check this out.