I think this is more of a bug than a feature...

Steps to reproduce:

  1. Set up the OpenGraph Meta module use the first 200 characters of the 'body' field as a default
  2. Set the Body field to use the 'Full HTML' text input
  3. Enter some style and/or script tags into the body field
  4. Note that the summary displays this HTML content in plaintext when shared via facebook

eg:

<style type="text/css">
#someStyleThatShouldBeHidden { somestyle: 10px;}
</style>
<p>Some text that you DO want to appear</p>

I know that entering CSS into the body of the document is not best practice, but sometimes needs to be done.

A proposed solution is to just ignore / strip out anything between <script></script> and <style></style> tags and comments <!-- ... -->.

Alternatively, there could be a configuration option to specify what set of HTML elements to allow through, eg <p><a><i><em><strong> etc.