We see signs of naivete, in Blogger Help Forum: Get Help with an Issue.
Why do I get so many spam comments, against my blog?and
Why was my blog deleted? I always remove spam comments!These blog owners do not understand that spam comments need to be removed promptly, marked as spam - not removed when convenient, or maybe just deleted.
Some blog owners let people comment anonymously, because it encourages communication, and brings them more readers - and moderate after comments are published, because it's more convenient for them, and again, encourages communication. They do not realise that the easier that you make it for people to publish comments, the more spammers will appreciate the open policy.
If you encourage comment spammers, by providing them a blog where they can publish their spam, even temporarily, you are leaving your blog vulnerable to spam classification, and to more spam comments.
If Blogger were to allow passive moderation without penalty, this would encourage more spammers to publish blogs, allow unmoderated comments, and provide a place where their friends can publish their spam without penalty. This would let spammers train the filters to be more spam friendly.
Given more spam friendly filters, more spammers would setup operations in Blogger - and give Blogger a well deserved reputation as a spammer haven. And legitimate blog owners would go elsewhere.
Blogger has to protect legitimate blogs - and the readers of legitimate blogs - by discouraging irresponsible passive comment moderation. Blog owners cannot let their need, to accumulate more readers, allow spammer activity.
If you must let people publish comments without moderation, and occasionally moderate published comments, you have to moderate frequently, and mark and remove published spam comments, before more spammers are encouraged to publish, on your blog. If you are moderating passively, and you start to see a steady flow of spam comments, this is a sign that you are not moderating often enough.
The more spam comments that are published on your blog, and the longer spam comments remain on your blog after publication there, the greater exposure that your blog will have to classification as a spam host. The question whether any resulting spam classification should be considered righteous, or spurious, is debatable.