It's always subtle, usually passive, and I've had it with most of the people I've been emotionally intimate with and in proportion to the degree of intimacy. The INFPs were the exception in that we instantly had a strong connection. To know what someone is feeling, I really have to focus on it, and unless it is a particularly intense emotion, it takes me a while to key in on. However, if it is intense enough, it will hit me like a wave, and then I have to figure out who it is coming from (unless it's one of my INFPs, who I always know the source if it is).
Do you have any kind of empathic connections with anyone? My INFPs tell me I'm not the only person they have those with.