The issue with the SoundCloud player not showing up for me that I reported here and here has been fixed. It took quite a bit of back and forth between staff and me, but the issue is resolved. Although they did not say, I had reported to them that the actual SoundCloud code was using XHTML param tags

<param>parameters_here</param>

and that WordPress was using self-closing HTML param tags

<param parameters_here /> .

Who knows if that was the actual problem or not, but Safari and Firefox on Mac were both pitching a fit saying there was a missing ending param tag. Obviously they were looking for XHTML versions of the param tag rather than the HTML versions, which puzzles me a little; both are – or should be – valid.

Anyway, many thanks to the WordPress.COM staff, and Sheri in particular, who stuck with this issue and finally whipped it.