Fun update:
I did a little experiment on my ride this morning. Rather than wave, I lifted my fingers on my left hand. Of the 60 or so vehicles that I gave the finger lift to while on the hoods, zero responded. Of the 20 or so vehicles that I finger twirled while on the tops, every driver waved back except for 2 that were clearly involved with their phones. So while on the hoods I'll be going back to the full off-the-bars wave.
Also, I saw three cyclists wearing matching gear that gave me a friendly wave and hello. It wasn't the usual group of cool kids, but it still made me feel good.