Are there any telltale signs that an academic job interview went well (or badly)?
Even if a department loves you, it's unlikely they'll show any overt signs (especially in an official capacity) because they want to maintain a reasonable negotiating position. 

But individual faculty are not always "with the program". For example, it's happened to me that someone said (during an interview) "I really like your profile and will be making a strong case to make you an offer". But while this might be flattering, it also depends on how much power that individual has over final decisions.