I'm with Josh. Now that negative doubles have evolved into their current common usage: a discussion about spades and NOTHING else (beyond the approximate number of hcp needed to warrant bidding at all), 2
♦ has to be a reverse, and even a moment's thought would show why.
If you don't play this as a reverse, in the sense of showing strength, ask how this differs, in bridge logic, from the auction 1
♣ (P) 1
♠ (P) ?
The answer has to be, in terms of the advisability of opener's rebid meanings, that it doesn't.
Assume that responder has a minimum, with shape such as 4=3=3=3. That is not beyond the realm of possibility.
Now assume that opener's 2
♦ shows no extras and is the preferred rebid on -2=2=4=5 hands.
We have just created a constructive sequence in which we cannot play our best suit at our best level

Nice theory, guys!
I remember, vaguely, playing in the Vancouver Bridge Club (quite a strong club back then) in the early 1970s, when my partner and I thought, erroneously, that we were pretty good. We then played negative doubles of 1
♥ as showing spades, with no reference to the other minor, and were told, very strongly, by one the older regulars (he seemed very old then, but was probably younger than I am now) that negative doubles showed BOTH unbid suits.
For him, and anyone stuck in that timewarp, 2
♦ is nothing extra. To modern players, it shows strength.
'one of the great markers of the advance of human kindness is the howls you will hear from the Men of God' Johann Hari