I ran the code to fix the BLOCKQUOTE [1] issue and as it turns out, there were 54 entries that needed further fixing due to the fix I just applied. I wanted the HTML (HyperText Markup Language) files to still be editable, and as such, I wrapped the contents of the block-level elements to fit within 80 columns, and the function I used did not take into account where it was safe to break on an HTML tag. So for future reference, I'll have to write a customize word-wrapping function to take into account HTML. As it was, I fixed all 54 entries by hand; some were trivial, some required going into the backups.
Ah, the wonders of automation. A human can mess up, a computer can mess up a lot. Quickly.
The other thing I learned is that the entity ' is not defined for HTML 4 (it is for HTML 5, and XML (eXtensible Markup Language)). This is important because I'm still using HTML 4 for my blog. Why not HTML 5? Because I'm not fond of the “living standard [2]” (read: changes whenever, meaning an ever-constant churn of updating HTML to maintain the standard du jour) and the step-by-step parsing rules [3] instead of a concise syntax. It also doesn't help that whenever I see WHATWG (Web Hypertext Application Technology Working Group), I read it as “What working group?”
[2] https://html.spec.whatwg.org/multipage/syntax.html