Thank you for your response. I know there is a plugin for self-hosted WordPress sites that allows you to create two headlines for a post and it will automatically monitor which one is getting more clicks and then go with that one permanently.
I know that sometimes in the past WordPress.com has absorbed into its native function new features that, at one time, required a plugin. I just thought it was an interesting feature when I read about it.
It could, theoretically, help boost traffic for every WordPress blog if they chose to use the feature. Anyway, that was my question, I was aware that it was used on the backend for features and such, I was just talking about post titles specifically.
I really didn't expect to get an answer but I wanted to ask.
Thank you again for your time.