Not only was I OK with that scene, I burst into tears the minute he did it. I've long maintained that we can't---on either stage or screen---go straight from Javert at the barricades to Javert committing suicide with no sign of his inner struggle; even "Stars" can't come out of nowhere. I've seen this handled in many ways during the musical. In the last performance I saw, the actor playing Javert (Andrew Varela) lingered over the fallen bodies at the barricade for several moments longer than one would expect if he had been just checking for Valjean. And he had this look of "what a waste" that showed the ice was definitely melting.

And so I agree with you: Javert is most decidedly not himself at the moment. I think it was good movie shorthand to indicate that EVERYTHING is changing for him . . . and it didn't occur to me until after I left the theatre, but it chilled me to realize that he may be even further gone than we thought at that moment, because "normal" Javert wouldn't have even considered letting go of that medal. So by the time he sang "Stars" I really felt like he'd reached the end of his rope, so to speak.

At any rate, the gesture made me cry buckets. And there was an almost seismic ripple of response in the theatre, so I wasn't alone!