I don't agree with the original author that this kind of superficial beauty is the best indicator of a lack of code quality. However, I like to use the following slightly devil's advocate-y argument that readability usually matters more than just about any other property of code, including correctness and good performance.
(In the absence of any standard definitions, let us take "readability" to mean "ease of extracting useful information from the code" and "maintainability" to mean "ease of making useful changes to the code".)
First, observe that most software projects are developed over an extended period and evolve over time. As a basic approximation, assume 75% of development time on such projects is spent performing maintenance on existing code. Assume also that half of that maintenance time is spent understanding that existing code.
Now, even if the code today has positive attributes such as correctness and good performance, those properties will only be sustained if the code's maintainability is good, because code is typically changed several times after it is originally written and if it is too difficult to make useful changes during maintenance then quality and efficiency will be reduced. Moreover, given the proportion of maintenance time spent on program comprehension, good readability is a necessary (though not necessarily sufficient) condition for good maintainability.
Thus, readability is paramount, because without it you can't have good maintainability, and without that you won't sustain any other desirable properties in the long term even if your code has them today.
The exception is when future maintenance of the code is low priority or irrelevant, for example if you're about to ship something that can't easily be changed once it's out the door, at which point obviously you care greatly about things like correctness and performance today.
The above argument doesn't say anything about whether "superficial beauty" actually affects readability as I have defined it. However, it would not be unreasonable to guess that it does, given that good visual design and typography have been shown to affect comprehension and reading speed under many different conditions. While I know of no research addressing the general influence of cosmetic presentation on bug count, there has certainly been research done into more specific questions. For example, in one study, using indents of 2-4 spaces measurably improved program comprehension relative to using either no indentation or indenting by 6 spaces (even though subjectively some programmers preferred the larger indent).
I haven't tried to present this as a rigorous argument with sources because I'm not sure the detailed statistics really affect the general gist of what I'm saying anyway, but FWIW all of the assumptions and figures I've chosen are based on extensive personal study of resarch literature, so they're definitely a reasonable starting point.
(In the absence of any standard definitions, let us take "readability" to mean "ease of extracting useful information from the code" and "maintainability" to mean "ease of making useful changes to the code".)
First, observe that most software projects are developed over an extended period and evolve over time. As a basic approximation, assume 75% of development time on such projects is spent performing maintenance on existing code. Assume also that half of that maintenance time is spent understanding that existing code.
Now, even if the code today has positive attributes such as correctness and good performance, those properties will only be sustained if the code's maintainability is good, because code is typically changed several times after it is originally written and if it is too difficult to make useful changes during maintenance then quality and efficiency will be reduced. Moreover, given the proportion of maintenance time spent on program comprehension, good readability is a necessary (though not necessarily sufficient) condition for good maintainability.
Thus, readability is paramount, because without it you can't have good maintainability, and without that you won't sustain any other desirable properties in the long term even if your code has them today.
The exception is when future maintenance of the code is low priority or irrelevant, for example if you're about to ship something that can't easily be changed once it's out the door, at which point obviously you care greatly about things like correctness and performance today.
The above argument doesn't say anything about whether "superficial beauty" actually affects readability as I have defined it. However, it would not be unreasonable to guess that it does, given that good visual design and typography have been shown to affect comprehension and reading speed under many different conditions. While I know of no research addressing the general influence of cosmetic presentation on bug count, there has certainly been research done into more specific questions. For example, in one study, using indents of 2-4 spaces measurably improved program comprehension relative to using either no indentation or indenting by 6 spaces (even though subjectively some programmers preferred the larger indent).
I haven't tried to present this as a rigorous argument with sources because I'm not sure the detailed statistics really affect the general gist of what I'm saying anyway, but FWIW all of the assumptions and figures I've chosen are based on extensive personal study of resarch literature, so they're definitely a reasonable starting point.