"A giant hack" is your name for evolved technology, as opposed to designed technology.
Of course, there's nothing truly "evolved" in software and nothing designed that didn't evolve, it's just two ends of an axis measuring a weird think like "control and unitary vision". An extreme of "evolved" technology are things like the browsers and PHP - the templating language that was never intended to be a programming language and somehow mutated into one (and I assign most of its success to being attuned to the "evolvability spirit" of our web). Most "well designed" or "well engineered" software that could have powered the web either failed miserably or never reached the point of being usable or just wasn't there at the right time.
I think there's a third path somewhere in this chaos, a path of software "designed/engineered to evolve", as opposed to "evolved" and "designed" software, a "nirvana" we should look for in this darkness. But in the meantime we can either embrace the "twisted creatures of webvolution"... or choose a different line of work :)
I think there is a distinction between a platform's authors adding more functionality and the platform's users abusing existing functionality to make it do something it was never meant to.
I would define the former as evolved and the latter as a hack.
Web technology seems to have developed from a little of each. People were using iframes to do HTTP requests so XMLHttpRequest was added to IE, People were using long polling so HTML5 now supports websockets etc. etc.)
I think the point of the grandparent is that the original standards were never meant to power applications, the web has changed but due to backwards compatability or old implementations the technology still has some warts.
An example of this is CSS, it's a fantastic system if you want to lay some static text on a page interleaved with some static images and style the whole lot. If you are trying to create a semi-traditional GUI or a page where you can't know the sizes of elements in advance then the shortcomings of CSS become abundantly clear.
I don't like the distinction because for a software whose developers respond to what the users are doing, after every hackish new way the users find to (ab)use it, the developers come and add things that make it easier to do the things done by "hacks" (but at the same time they also need to keep the hacks working). And if the "users" of a software like the browsers are actually developers, it's obvious that they are not going to expect for features to be properly implemented, they will just (ab)used whatever half-assed features they can find.
...in my view, if you can clearly see "the distinction" between authors adding functionality and users abusing existing functionality for new purposes, it means that one party is clearly moving too slow: either the "users" are too slow to discover new ways to adopt and (ab)use the new software or the developers are working to slow and the users-developers need to do too many ugly hacks because the features they need take too long to be released and standardized (unfortunately the current state of web-development seems closer to this state of affairs).
But there are possible solutions: I think things like standardization could be accelerated by having "tzars" in all committees (people that can just choose by themselves how some things over which they have authority get to work without needing a consensus or to justify to others why they choose one way) - I'm using the word "tzar" as in Haskell's "syntax tzar", the guy who could just choose what syntax a certain language feature needs and end the discussion right there because nobody had the right to contradict him [1] (I consider H's design-by-committee the only example where a committee did something mostly right and I wish similar "committees" would work on things like CSS and new ECMAScript versions...). But again, if standards evolve too fast, implementors will have to play catch-up and end-up with half-done implementations, which today happens even for sloth-slow evolving things like CSS.
...but of course, the real "root of all evil" is the backwards compatibility requirement, but we can't get away from this.
...and I know, some people will want to burn me at stake for screaming the "we're not going fast enough" heresy about web tech :)
Of course, there's nothing truly "evolved" in software and nothing designed that didn't evolve, it's just two ends of an axis measuring a weird think like "control and unitary vision". An extreme of "evolved" technology are things like the browsers and PHP - the templating language that was never intended to be a programming language and somehow mutated into one (and I assign most of its success to being attuned to the "evolvability spirit" of our web). Most "well designed" or "well engineered" software that could have powered the web either failed miserably or never reached the point of being usable or just wasn't there at the right time.
I think there's a third path somewhere in this chaos, a path of software "designed/engineered to evolve", as opposed to "evolved" and "designed" software, a "nirvana" we should look for in this darkness. But in the meantime we can either embrace the "twisted creatures of webvolution"... or choose a different line of work :)