The comment section is as (or more) important than the content of a blog as it creates a sense of community blogs thrive on comments. With that in mind I encourage you to comment where you see fit. On this blog I allow for anonymous, OpenId and Name/URL comments along with commenting by Google account holders.
1. I do and will delete spam.
2. Feel free to link to an entry on your garden blog in your comment if it is on topic to the post. To create a link that doesn't fit within the comment body use this method: <a href="http://www.gardenbloggers.com">Garden Bloggers</a> it displays as Garden Bloggers. Just copy and paste that into your comment and change the URL and "Garden Bloggers" to suit your needs.
3. Drive by SEO links in the comment section by spammers will be deleted. This is not a good way to build up links and you people should be ashamed of yourself for charging naive website owners for this.
4. I've enabled Name/URL comments. If you want your comment to link directly back to your blog without going through your profile use this method. Here is a screen shot of how it works. If you have more than one blog and want to keep your profile private this is a good option.