David,
The comment from Abbie (I believe it was) about opening comments was partly what generated this question to see what others do. It's complex: one one hand, opening comments invites spam, snarkyness, and more. On the other, moderation or registration restricts it. Why I asked "why."
But then again, I don't think google rates relevance by how many comments are on a blog, but rather how many external links reference the blog - which would be comments elsewhere.
Joel, thanks. Been using a licensed version of Akismet for years.
Charly, thanks. I have comments moderated. I was asking what other people do and why to get a feel for the opinions of the community at large.
Edward, did not know that (time-tracking). But does google know what they are doing there? In other words, couldn't stay-times also be lengthened by writing longer articles or offering more pictures to look at?