The biggest swing I saw had an amplitude of 1.4 volt - that's huge on a 3.3V power line. Still, it looks worse than it is. In about a microsecond the voltage was pretty much back at 3.3V (on average) and had I measured where the 3.3V enters the main circuit board (instead of directly on the outputs of the voltage regulator) the swing would've been less. My NR3 never acted funny nor did it hang while I was doing this.
Mine isn't currently modded, but I might do it. As long as that capacitor is soldered on carefully (and correctly, mind the polarity), the mod can easily be undone. The cap itself costs like 0.15 euro.
Unless you really trust yourself, have some good soldering skills and a fine-tipped soldering iron, don't try to mod it yourself - it'll likely end in tears/frustration. Find someone who does have the skills and equipment (a soldering iron with a 3mm tip - or less). It's a 2 minute job, so if you know someone who could do it, I doubt they'd mind doing it.
Edit: what this shows is that interference on 120/230 volt might be able to reach the processors in your Nord. Ideally this interference would be filtered out (better than it is now). Where I live (the Netherlands) there isn't much interference on the mains power (which is why I had to create some with that vacuum cleaner), but it might be different in your area. I also tried plugging in the vacuum cleaner into a power socket on the other side of the room; when I did that and started turning it on and off, I wasn't even really able to see that on the output of the 3.3V regulator.
