I guess this is supposed to be ironic. Contrary to what you said, the compiler and _nimsuggest_ doesn’t use the same rule. I have no time to find the reason for this, but one thing is sure: if _nim_ binary is in /usr/bin, the compiler does the right thing and expects the library to be in /usr/lib/nim while _nimsuggest_ expects it to be in /usr/lib.
When I have time, I will create an issue for this. At least, I expect that someone will check and give me a better answer that yours.