I really don't have much experience with the ATmega32U4 on the Micro, other than simple projects using the keyboard/mouse emulation. It's strange because the product page very specifically says:
Note that the SPI pins are not connected to any of the digital I/O pins as they are on the Uno, they are only available on the ICSP connector and on the nearby pins labelled MISO, MOSI and SCK.
But the pins work fine for me using digitalWrite() and digitalRead(). I can't imagine what the reason could be for writing that sentence and also for not numbering those pins on the silkscreen.
In fact pin 17 (SS) is LED_BUILTIN (the RX LED on the board). I'm not sure how that LED is connected so that might be something to consider if using that pin.
If you look at the Pro Micro board:
They do have pins 14-17 labeled as such.