Currently there are no moderation options for wall, blog and gallery comments. You cannot set them to be pre-moderated by default per user-group like you can forum posts or gallery images.
If the option existed it would be a good start to combating spam on Woltlab in the app comment system.
There is also the need to allow these comments to be used for the new WCF2.1 user-group promotion feature. Right now you can promote someone with X number of (pre-moderated) forum posts. Ideally you need to be able to promote based on approved comments, wall, blog or gallery individually too.
The lack of these moderation options creates a real open hole for comment spam. The is no way around it. You either have comments on or off and when on unless you watch every image, blog post or profile wall you will never see the abuse.
If you have wall, blog and gallery commenting off by default you will suffer content growth unless you promote users based on a totally different activity, which makes zero sense. This is a problem because some users may intend to comment in the gallery with no intention of forum involvement. They will be stuck in no-comment limbo forever.
As a side note the stop-word censorship feature also doesn't work in wall, blog or gallery comments. I see the ability to guest comment has be added in WCF2.1. I doubt anyone in their right mind would turn this on with so little control over what people can post live to site.
I think such an issue needs more exposure and hopefully constructive dialogue with the developers.