Enjolras stifles the brief twinge of irritation at that expression, which seems to him sardonic. Whether it is or not, there's no point in responding.

There are other things he might say to one of the others. But to Grantaire, now and here, what he says is, "What do you think of all this?"

It's a serious question. He's not holding out great hope for a serious answer, but there's always a chance.

And in the meantime, there's a delta-marked archway that might be a door just ahead. Enjolras slows slightly to let Grantaire catch up; they may as well pass through together.