It must have been bad. Sirius already knew that, sure, because Remus said so, but the fact that he couldn't even prompt some sort of physical -- well, anything-- was more telling than anything else. Because usually they were sort of just... all over each other. Just in little ways, but that didn't make it less obvious.
He hated it. Absolutely loathed whatever was going on here and he half didn't want to know because Sirius had never done particularly well with dark emotions. But there was no not knowing, he figured. Because Remus had a point, maybe he could go back to the time he came from and stop Remus from ever needing to make the faces he was making now.
Maybe in some other weird universe (it was hard to wrap his head around) he'd never have to be sad at all. So. Yeah. Maybe he'd been stuck in Gryffindor for a good reason after all. He wasn't about to turn away from bad things just because they were bad. "Tell me." He said-- urged, really -- even though it sort of hurt his stomach to do so.