I tend to find waving rather mark-specific on the whole.
In other words, if I wave at a driver in a mk3, like mine, I often get a positive response, but wave at any other mark, and more often than not, I get blanked.
Having said that, a couple of weeks ago, I was driving through Frome (my home town), and spotted a bright yellow mk.2 Arizona behind me. We both had our lids down, and as I took off from a set of traffic lights, waving like crazy as far as my arm would stretch above my head, he did the same, before turning off in another direction.
Surely people enthusiastic enough to buy an MX-5, whatever version, would be aware of other variations built over the past thirty years - perhaps not.
Oh well, enjoy the summer my friends - hasn’t it been fab so far ?