Question: how do you know when the thread is locked? I remember that there used to be little lock symbols beside the threads if it was locked, and even a quick explanation that the thread was locked. I don't know if its because I'm on IE, or at work, or what, but  I saw nothing that let me know the thread was, in fact, locked.

In the thread list, there is still a padlock on locked threads (or at least there is when I look - Firefox 36.0.4 Windows 7 etc.) That could be down to IE I suppose - I don't use it myself

Frank, none of the icons show in my version of Firefox - same version as yours. I'm quite certain it's from browser addon products I use, but I most certainly do not intend to change my browser settings just for RO.  Especially, given the recent Man In The Middle attack they have experienced.

I care much more about browser security than itty bitty icons on a website.

I have Adblock and Noscript and that's it - could well be a firefox add-in though, there's a lot of them :)

It's the NoFlash addon causing the issues with the icons.  Probably the same for IE - Flash addon not enabled. Again, for me, turning it on means compromising my browser security and I have no intention of doing so.  But, that's my choice.