He is momentarily confused by Frisk pausing to type instead of speaking, but - oh, well, it doesn't really matter. He waves back in return.

"Good to see you, Frisk. I am Signless," he says, and his alien accent is apparent. Reading and listening are both easier for him than speaking. He assumes he'll get better at this with time. "Has the night been good?"

He's a little bit concerned about their apparent youth, but not because he doesn't believe they can do it. It's just harder, is all.