And really, you can talk and ask for clarification from people you're flirting with. Heck, asking "are you flirting with me" is itself a reasonable flirt-and-escalate move. Being explicit can kill the mood for some people, but if you're not actually sure where in this dance you are or which direction it's headed, it's generally safer than risking unwanted boundary crossing.

If you need verbal feedback, you're probably better off finding out fairly early whether the person you're flirting with is comfortable with questions or not.