Arf! Arf! Arf!
(HELLO in human terms),
Seriously, I've noticed something exceedingly frustrating in the process of moving content from Theme to Theme trying to find the Holy Grail of perfect display.
What I've noticed is that some themes provide Featured Images as an initial link to a single post page, while other themes start that process and then also include that Featured Image at the top of the single post. When you test themes that say that they include Featured Images, you never know what the end result will be.
Is there a snippet of code that I can paste into themes that insist on embedding the Featured Image into single post pages, so I can prevent that from happening regardless of the intent of the theme developer?