&gt; Amaya, after all, didn&#x27;t prevent HTML 4 or CSS 2 from having unimplementable sections.<p>Amaya was always in an odd place — it was a &quot;testbed&quot; and not a reference implementation. (Also, if you actually look at the parts HTML 4 that required anyone to do anything, you end up with things like dbaron&#x27;s table (as in, a desk) implementation of it: put quotations mark at either end of the table, and whatever HTML you put on the table, it has fulfilled all the requirements of the standard.)<p>But yes, the underlying problem of different approaches is a large part of the reason why you want multiple implementations — the other large part is you want <i>evidence</i> the standard is clear enough to lead to interoperable implementations. These are the two big reasons the W3C now require evidence of two, distinct, interoperable implementations of a specification to proceed down the Recommendation track beyond Candidate Recommendation (i.e., to Proposed Recommendation)… and this is the reason why so much around the W3C takes so long, because people by and large don&#x27;t want to fix ancient, obscure bugs which are often time-consuming to fix for the sake of the standard progressing.