that's a good point you bring up

I think it is more of a Fe thing than a Fi thing because there's nothing really "inherently offensive" about the comment (or contrary to Fi values in the sense of norms). Its not like joking about someone's dead mom or something. Rather its implied that it had a negative effect on the mood simply because it understood its own complimentary "insight" (factual connection-- Te observation) without consideration of how it would come across which in fact served to lower the energy not raise it, that kind of counter productiveness seems to be Fe polr because it was "100% sincere." If he was sarcastic it seems like it would be more Fi polr because it would be taking a direct shot at the person while bringing moms into it (ethic of relations, expense of one's own mother in a certain irony). In other words if it was intentional you could say it was Fi polr because it had the desired Fe effect; here it unwittingly had the reverse of intended Fe effect without directly implicating a lack of Fi value (although at first it appears like it might because its bringing moms into it, since it was sincere its not actually really being a dick about anything in terms of Fi)

also you gotta think in terms of Fe polr as a product of Te creative, hence it seems like Fe polr because this seems like a more Te statement

whereas Fi polr is more a product of Ti creative so a comment in terms of that would be if it were sarcastic and implying a Ti principle "only moms think thats a nice jacket" i.e.: you're out of step generationally with your fashion choices