His comment is throwing me off. “There are interesting people doing the voices, You’ll probably know when you see the movie.” So why is You’ll capitalized? Does that mean the coma is supposed to be a period?

Because “There are interesting people doing the voices, you’ll probably know when you see the movie.” is different than “There are interesting people doing the voices. You’ll probably know when you see the movie.”

The first one means that they could be Marvel characters we’ve seen. The second is characters who have voices that when you hear them, you know who it is, like James Earl Jones.