I see what you mean there, and this may be a bug with the Send to Kindle plugin. It looks like Facebook is picking up information out of a Twitter meta tag to display an excerpt:
<meta name="twitter:description" content="Send to KindleFor some strange reasons that have to do with my health insurance company’s bureaucracy, I’m now a resident of Florida for medical purposes. Which means I’ve had the unpleasant task of finding new doctors for all the stuff I need, ophthalmology being one. Given the aging population that tends to reside in Florida, [...]"/>
This tag is generated by the WordPress SEO Plugin plugin you have installed, which internally calls get_the_excerpt
. Most people do not write up an excerpt for posts, so WordPress grabs the first 55 words of the post content and uses that as the excerpt. The problem we have is the button plugin works by appending to the content.
To make a long story short, you are seeing the bare text of the button after the HTML tags have been stripped away. The short term-fix you can do is to set the button to display after post content, and I need to come up with an appropriate long-term solution.