So after all these years, and especially since I can no longer use Renoise 2.7.2, I confirmed that something DID break... and MUCH sooner than I expected it to be.
So remember when I said that I had my concerns about Renoise 2.8 breaking things? Well, I used FCxx, a global command in the effect column, to perform a fade out by directly setting the master volume (though I used it in the track where I figured it would fit). This very command was cut in Renoise 2.8 and later. So for those of you trying to use the raw file and wondering why the fade outs in particular were not working, that's why. At least my mistrust was justified from day 1 in hindsight when it came to introducing playback inconsistencies, accidentally or not.
I also determined that something got thrown off in the volume balance when it came to sending a track over to another one for processing, probably because of a bug that caused the audio signal to get amplified.