Man you really like to obsess over shit don't you, I can be like that too sometimes I have to stop myself from making threads about every little thing that pops into my head.
Sounds like you answered your own question on this one brother.....
Keep in mind that they aren't going to pull any punches about nicotine because it relates to smoking so any little thing they can pick at about it will get included as a side effect, if you searched enough you could probably find somewhere that lists satan worship as a side effect of nicotine just because it's put into the context of smoking. Kinda like how randomly researching the mainstream for PED use will make you believe that it will instantly kill you after it instantly turns you into barry bonds, being dramatic obviously but same concept. But don't get me wrong I am not defending smoking at all i'm just pointing out that the reason you can't find anything direct in regards to it hurting kidneys even though it's listed as a side effect in your research of nicotine probably means it's not directly harmful and just a lumped in side effect with all the other bad stuff to do with smoking.
I don't know personally if it is or isn't harmful for kidneys I've never researched that, I'm just the pointing out the perspective on it.