Just wondering if CRs, LFs and <script> tags should be stripped (only when posting in HTML mode) before placing it in the og:description header.
Negative, the way things work for all posts is to run things through the filters, the easiest of which is strip_tags (well, a custom form of it, see the strip_tags_special function in libs/bbcode.inc.php), which is removing tags as its supposed to, but is being left with the additional content within the tags in your post as post data (as the stripped tags are being removed as they are supposed to be).
HTML posts and HTML with UBBCode are parsed differently, BBCode posts will not filter CR and LFs.
If linking to offsite JavaScript is a requirement, you should look into custom bbcode tags; your special use of the HTML mode (to include JavaScript) is really out of the scope for what these default tags were written for (which was formatting), so if you want to keep the stock code in place and not use custom bbcode tags (with its default behavior) I'd recommend just leaving the og:description tag commented out.
