Unhelpful feedback

The CentOS project just tweeted an announcement :

The feedback was mostly positive, but two negative responses caught my eye.

The first:

Curved edges on this do not scale down well at small sizes. It's a very busy design for something which will likely be used a lot on screen/small sizes. A step in the right direction but needs more refinement IMO. Solved the colour repo headache, but potentially creating another.

Feedback is specific and seems to indicate actual expertise.

The next:

Feedback is useless, and incorporates a personal attack (designer should be fired) which is just rude.

I’m left wondering if this person thought that this was in any way helpful or that this is in any way an appropriate way to engage with a stranger. Would they talk with a human in person like this? Do they have any friends?

And even without the rudeness, the response is completely worthless and unactionable. So, one deeply unpleasant person didn’t like it, while 100 others did. Why should I care?

I also wonder if there is a way to respond to this person without returning their vitriol.