To "dun with faint praise" is to insult something by saying an ostensibly nice, but very weak, thing about them as if it's the best thing you could say.
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More or less.
I believe IQ measures something semi-stable, but whether it's a valuable or even coherent something is a question I've not seen answered adequately.
Does the size of your nose matter? It's also an accurate measure, but unlikely to matter much outside of glasses.
It's also a question of how much surface area of what it claims to be the problem space it is actually covering.
Intelligence quotient is a VERY hubristic label for "well, we think these are some measures of cognitive performance anyway..."