I disagree. The person that will impede his ability to accomplish actual work because of his subjective aesthetic preferences is substantially less "mentally capable" than a person that will tolerate a bit of ugliness for greater efficiency. Again, it's a matter of degree because there are some programs that are so "ugly" that they are unusable, but the grandparent's specific example was Safari v. Firefox, and while Firefox may not conform to Apple's aesthetic standard exactly, it's far from unusable. The GP admitted that both Firefox and Chrome were superior to Safari in tangible ways that affect productivity, but that they continue to use Safari because they think it's prettier. I cannot comprehend that POV and have no respect for people who hold it, and that expands outside of software too.
I can see you've decided to ignore what I actually said and instead substitute your own version.
I'll tell you what I can't comprehend – people who apparently find it difficult to accept that other people have differing priorities to them, and aren't mentally subnormal as a result.