[Commentor] LC-289 Ian Jacobs [Comment] * How do you define a "deficient" implementation? It sounds quite subjective to me. Do you mean implementations that do not conform (strictly) to standards? Otherwise how would you classify something as deficient or not? Do you mean "known bugs"? [Commentor reply] yes [Working Group decision] 
We have added a clarification of the intended meaning of deficient: "By deficient we mean non-support of mandatory features of a relevant standard or recommendation and other bugs or errors in implementation."