I checked in my list of plugins, and I have nothing that seems like Related Posts or Similar Posts. Yet, at the end of my posts I find two very similar sections titled as such. Any idea how to turn one of them off, and how to understand what plugins are responsible for generating them?
Similar posts section has following comment in page source
<!-- Similar Posts took 18.313 ms -->
which quick search identifies as belonging to Similar Posts plugin.
Nothing to identify "Related" section by. I'd try to search sources for that heading.