Welllll ... OK. Fish may not mind nitrates directly, but the fact is if you have too many in your system there will be unpleasant consequences nonetheless, it is better to avoid a buildup, which was the point I was trying to make. Also I sort of used the term "nitrate soup" simply as an analog of "water with a high dissolved organic compound" which realistically will include other byproducts/endproducts/whatever besides only nitrate.
Nori does seem to introduce phosphates as well:
http://canreef.com/vbulletin/showthread.php?t=12625&
I guess the point I was trying to make is that if you find your tank system in unable to cope with the bioload of the fish being fed, that it is an indication that things may need to be adjusted or upgraded (larger tank, more LR, stronger skimming .. whatever ..). One needs to take a balanced approach.