There are obviously benefits and drawbacks to having comments on your blog. Akismet takes care of most of the SPAM for WordPress users, but SPAM is not the only type of comment many bloggers do not want on their blogs.
There are always dissatisfied visitors who feel they have the right to be abusive, call names and use offensive language which you may not want appearing on your blog. There are also users who tend to write highly off-topic and borderline spam topics. Then there are people who just plain disagree with what you’ve said. Now there are a few of these that you will want to deal with, but don’t be too quick to delete a comment that is critical of you or your statements.
There are also other options for keeping SPAM comments at bay. One of the blog networks I write at uses WordPress Multi-User without an Akismet liscence so our only methods of combatting spammers is using either recaptcha or WP’s built-in comment moderation feature. Personally I get by just using recaptcha, a very small number of human spam gets through, but I am OK to simply edit any bad links out of those few comments when they pop up. However, there is a significant number of people using both which goes beyond my understanding.
I think the whole reason for having comments is because it encourages the community aspect of blogging. There is also nothing more rewarding than having someone leave their thoughts and add to the conversation you have started. Since the spam is already reduced and, in most cases, eliminated by recaptcha, the only reason I can come up with that the blogger enables moderation is that they don’t want any comments they don’t agree with going on the blog.
Personally, I don’t delete negative comments. I don’t even edit them. It is my personal feeling that removing people’s opinions, just because they differ from my own, defeats the purpose of having blog comments in the first place. It is also my personal opinion that if my post truly does contain sound information that holds any water at all, it should be able to withstand a little disection from the readers. If anything, seeing that their comment is being held for moderation makes users feel unwelcomed, untrusted, and like they can’t say what they want. When I see that my comment needs to be approved before it gets posted I rarely come back to check if it has been or not. I don’t think I am alone on this.
The first-time commenter has been struck by something you said, maybe it is their first time at the blog, maybe they have been there a few times and never felt the need to chime in. For whatever reason, this is the reader’s first time commenting and if they find that they have to pass some sort of screening process, especially after already going to the trouble of entering a recaptcha answer, this can be highly discouraging.
It may be a little more legwork, but you will likely retain more commenters by allowing them to speak their minds and weeding out what needs to be afterwords.