The previously posted answer by ermanen probably captures well the practice of the majority of the regular contributors to this site. They are generally reluctant to post something like 'There is no answer' as an answer (although they may be willing to post it as a comment), even when they are confident that this is true, because they feel that such an answer would be too simple, too unsophisticated for this site. They would be embarrassed to receive reputation points for an answer that is so easy to make.
This practice may seem honourable and dignified, but it has a downside. Suppose that somebody posts a single-word-request for a word with some very definite, precise meaning. The knowledgeable people know that there is no such word, but, for the reasons outlined in the first paragraph, don't post that. So far, so good: as long as no answers are posted at all, their absence conveys that there is no word that the OP was seeking. The questions of this sort, however, usually don't remain entirely without answers. Somebody will, sooner or later post an answer suggesting a word that does not really fit the meaning that the OP wanted captured but is loosely related to it, somebody else will offer a very broad term that includes the OP's meaning but is not limited to it, somebody will create a new word and propose that it be used for the purpose. None of these answers, some of which may be upvoted, will be as good as 'There is no such word', which nobody will post.
Somebody who comes to that page in the future will then see that the question has a number of answers and may well be led to think that the most highly upvoted among them is the correct one. The practice of abstaining from posting no-answer answers thus misleads the future visitors to the page, which is at odds with the main purpose of this site.
One compromise that takes into account both the reasons for and the reasons against posting no-answer answers would be for the regular contributors to adopt the practice of posting wiki-answers saying something like 'There is no answer', whenever that seems to be the truth. Their being wiki-answers would show that those who post them are acting with proper modesty and respect for the standards of the site, and are not claiming any credit for such short, simple answers. The main purpose of these wiki-answers would be to provide a 'hook' for the upvotes by everyone else who is also confident that there is no answer. If it is true that there is no answer, then it is to be expected that this wiki-answer would be more highly voted than the not very good answers offered elsewhere on the page, and that would help to ensure that the future visitors are not misled by these other answers.
(What if, after that no-answer answer is posted, somebody proves that there is, in fact, an answer? In that case, the no-answer answer could be downvoted, and possibly deleted; again, its being a wiki-answer means that nobody's reputation would be affected.)