Best Digital Interface

I'm not familiar with your RME, I never heard of a dac that didn't reclock S/PDIF. I'll take  look at the manual.

30.3 Digital
  Clocks: Internal, SPDIF In
  Jitter suppression of external clocks: > 50 dB (2.4 kHz)
  Effective clock jitter influence on DA conversion: near zero
 PLL ensures zero dropout, even at more than 100 ns jitter  Additional Digital Bitclock PLL for trouble-free varispeed ADAT operation
  Supported sample rates for external clocks: 44 kHz up to 200 kHz
 Internally supported sample rates: 44.1 kHz up to 768 kHz

Maybe I'm a bit dim, but this section of the manual states that this DAC controls jitter of all formats.

Without USB isn’t the clock in the Node 2 running the show?

The master clock in the RME DAC is always running the show. It reclocks each digital signal you choose. S/PDIF is high quality and the most practical format to use.

@classdstreamer,
Good comments, so the DAC is not actually reclocking SPDIF, only suppressing jitter. That’s a pretty vague statement.
Like you, I’m using an iFi to reclock the stream from my Node2i and the improvement is audible. I recommend adding a LPS.
Even with advancements in jitter reduction, I want the master clock at the destination and not at the source.
Thanks for the comprehensive explanation.

@auxinput

The S/PDIF interface requires the data to be clocked from the source. This is the only way it will work and it is part of the interface specification

Why would a DAC in this day and age rely on a source's data stream which could be flawed rather than use an internal clock? 
It makes sense to not include an internal clock if a master clock is being used, as in studio setups.

These specs indicate that jitter is being suppressed internally, so there is some device reducing any jitter.

  Clocks: Internal, SPDIF In
  Jitter suppression of external clocks: > 50 dB (2.4 kHz)
  Effective clock jitter influence on DA conversion: near zero

Rsjaurr,
Yes, I know. That's the point I've been trying to make.
 
The OP posted from the manual...

With USB the internal clock is used, with SPDIF the external one".

Isn't that saying if SPDIF the RME does not "own the clock"

This statement indicates that only USB is being reclocked.
But, according to the spec sheet I posted, all signals are being clocked inside the DAC. 

My earlier post was to say it doesn't make sense to rely on the stream from the source without correcting it. I believe this Dac is designed to reclock all digital streams.