The reason why you want it at that height is so that if people get up from the table or lean over it to grab something, they don't hit their head on it. Also you want to be able to put things underneath like an arrangement or candles and such and not have the fixture get in the way. And it's a matter of looks. If it looks ok to you, then it's fine.

Well, also, you want to be able to look across the table at someone and not have the fixture in your line of sight.

Fwiw, I need to lower our DR fixture and I was curious about how low that would be. I took the --- admittedly unscientific --- approach of having my 11yo measure from the table to the top of my head when I was seated . That was about 26". I am 5'9. So it would seem to me that 30" would be the minimum height for someone 6'1, not a rare bird at all, at least not in our families.

That is way too low mate. The lighting from the fixture will be very distracting and would just make it harder to see or talk to someone on the other side of the table. If you are less than 6'2 I guess that's ok but if you have tall family members then that would be a problem.

if the fixture only has a diameter of 17", hitting heads on it probably won't be so much of an issue... but, sight lines probably will be...
I wonder if it looks like it should be lower partly because it is a bit too small??? 17" ht and w is quite small for over a dining room table unless your ceilings are really low or the overall room is very small...
if you have an average sized dr and ceilings that are at least 8', maybe hanging it lower is the best way to have the chandelier look it's best!

Thank you all so much for helping me! I never really thought about tall people getting up from the table but that makes a lot of sense. I'm only 5'7" on a good day but DH is 6'3" and my little brother is 6'7" (he's gonna have a hard time in my house no matter what). As far as sight lines - I sat at the table and it doesn't impede vision across at all and the light doesn't shine in my eyes so I think we're ok there. It's not a very bright light to begin with.

The room is on the smallish side and it's got a thoroughfare running through it so I cheated the whole table buffet assembly to one side. We have 8 foot ceilings and I would say the entire space (minus the walkway) is only 9 x 11 - an 8x10 rug fills it out perfectly. The table is small too, only 40" across I think. When I did the calculators online they told me 17-23" was a good place to start based on the size of the room. The chandelier is pretty visually heavy so I err'd on the small side.

Anyway, considering all your input I'll just leave it where it is. Thanks again!

If it works for DH, that is going to work for most of the population. DB is probably used to things being off for him!