Thanks everyone!

This was not the first time that my failure to search for an answer was due to my lack of knowing what words or terms to look for.

That said, I only found the actual words (see title) in only one unhelpful thread in all of PPCGeeks. Even the OMJ post only refers to the issue as "test". I did find a lot more at our friends over at xda-developers but they were usually talking about phones other than the Diamond.

Fortunately I was paranoid and backed up everything hours ago because I didn't read the post warning me about the hard reset until after-the-fact.

Everything seems cool now.

Cheers, Henri