I assumed one can mix and match HTML in markdown?
I checked, htmlscrubber is really disabled. So it's not scrubbing anything. Really.
What is going on is you have found a bug in markdown. If you feed the file into markdown directly you will see a bunch of weird hashes like 67255d9b2a988139c95269498399f10a in place of your html, so this is like Debian bug #380212 but that was with the other version of markdown; I have not seen the current version behave this way before.
One workaround is to wrap the html in a span tag. Another is to switch the page from .mdwn to .html and enable the html plugin. I guess I'd pick the first if I were you.