"Similar Posts" is not a Blogger feature - but there are several third party services which provide this feature, generally used in blogs which consistently use photos in the posts. This feature will be more useful, with photo rich blogs - and less useful, with label rich blogs, and blogs which link to other posts in text (like this blog).
We see occasional reference to this feature, from people who are not aware of how search engines work, in Blogger Help Forum: Get Help with an Issue.
Why is my "Related Posts" display blank?and
My "You may also like:" accessory links to deleted posts!These blog owners are not familiar with how search engines index posts.
"Related posts", "You may also like", and similar accessories are specialised search engine indexes.
The Google "Custom Search Engine" lets you search your blog, against key words, supplied when necessary. "Related Posts", and similar features index your posts according to subject matter - then compare a post being displayed against similar posts in the blog, and display a list of 2 to 5 similar posts.
That's the difference between the Custom Search Engine, and "Related Posts" et al. The similarities are what is most telling. Each of these accessories depend upon search cache - and this dependency creates cache latency.
Cache latency means
- If you rename your blog, the blog has to be re indexed.
- If you delete posts, the blog has to be re indexed.
The larger the blog, or the more posts deleted, the longer it can take to recover from a change. Renaming a newer (smaller) blog, or deleting a few posts - and recovery can take less time than renaming an older (larger) blog, or deleting more posts.
Search engine cache is just one more detail, in the process of renaming or of deleting posts in a blog - and one more need to plan a rename, or a deletion.