Earlier today, I was in MPSIMS. There’s a post count thread by Lobsang that Cajun Man locked down.
I swear I saw the lock icon suddenly appear over the thread icon.
Did I really see this, or am I crazy?
Why would you assume the two possibilities to be mutually exclusive? 
Okay, crazi-ER.
I don’t think this happens live. Rather, I’d hypothesize a sort of illusion: If you hadn’t had a locked-thread icon recently, it would have to be loaded from the site instead of pulled from your local cache. So all the regular icons appeared, and a second later the locked icon appeared after having been downloaded. If you saw it only out of the corner of your eye, your brain may have misinterpreted its appearance as a switch.
Just taking a guess about what might have happened.
I don’t think you can have things appear live on this message board. It’s just an ordinary web page, and you only get updates when you refresh the page or click a new link.