Should these keywords be banned?

@adrian Those "not-on" keywords have not been maintained, though. Many of the instances where the keywords have been used are no longer accurate. And who would be responsible for maintaining them, anyhow? That is part of the problem with those keywords -- they have unknown expiration dates. 

Another issue with the "not-on" keywords is it is rarely a good idea to frame a keyword starting in the negative. These keywords remind me of the "no-abnormal-relationship" keywords. And where would it end? Could there also be keywords like "not-on-vhs," "not-on-netflix," "not-a-streamed-movie," etc.?

Finally, the "not-on" keywords have nothing to do with each title's plot.  Keywords are primarily intended to be "plot keywords." There are of course many exceptions to that rule, but a non-plot keyword should be pretty good in order to be justified as an exception. In that sense, these keywords remind me of the dumb keyword "film-released-during-covid-19," a keyword that will not age particularly well. 

@keyword_expert I agree that such keywords are inappropriate. I'm reminded of Mike D'Angelo's review of Pascal Bonitzer's Rien sur Robert (1999):

The phrase Rien sur Robert ... isn't so much cryptic as it is pointlessly accurate: it translates roughly as Nothing About Robert...and, sure enough, no character by that name ever appears in, or is alluded to during the course of, Bonitzer's directorial début; it's rather like calling a Civil War epic No Faxes, No Modems.

Keywords ought to describe what is in the film, not what isn't there. I could understand a rare exception such as "no-dialogue", but I wouldn't support the "no-lgbt-character" keyword nor others you mention such as "no-product-placement," "no-cigarette-smoking," "no-sex-scene," "no-violence," "no-nudity," "no-female-character," "no-male-character," "no-transgender-character," "no-black-character," "no-white-character," "no-teenage-character," "no-elderly-character," "no-mentally-ill-character," "no-disabled-character," etc.

The other night NBC showed "Christmas Eve at St. Peter's Basilica" with Pope Francis celebrating mass. Among the actual IMDb keywords that could theoretically apply to this show are "no-alien-threat", "no-bones-broken", "no-brake-lights", "no-breakfast", "no-cowboys-in-this-film", "no-jetliner-in-this-film", "no-laugh-track", "no-parachute", "no-question-in-title", "no-senior-prom-date", "no-student-protests", and "no-wire-hangers", because, indeed, the program didn't have any of those. And I'm sure we could think of others, like "no-atheism" and "no-car-chase", since the show didn't have those either. But it would be silly to submit any of those as keywords for this program.

Note: In most cases, where the absence of an item is an important plot point, I would recommend phrasing the keyword in the positive rather than in the "no-" form. For example, suppose that a movie began with the main character waking up and finding that his passport is missing. He spends the entire movie searching for the passport, but he still hasn't found it by the end of the film, and in fact there is no scene in the film where any passport is shown. For such a film, I would recommend using the keyword "passport" instead of "no-passport". This would reduce the chance of the keyword "no-passport" being applied to other films where passports don't appear because they are not relevant to the plot.

@gromit82 Very thoughtful response, Mr. Gromit.

Your example list of "no" keywords for "Christmas Eve at St. Peter's Basilica" is very funny, and is also very effective in illustrating why "no" keywords shouldn't be used. 

I also agree with you that sometimes it does make sense to use a keyword for a plot device that only "appears" in the title via its absence. I have done exactly that many times.

In your specific example, I would add both the keywords "passport" and "lost-passport." 

In your example, some users would use the keyword "reference-to-a-passport." I think that would be wrong, and I will explain why.

One pet peeve of mine is when fellow users mistakenly believe a plot device requires the prefix "reference-to" if it is a physical thing or place that is "referenced" but isn't literally shown on the screen. 

The inappropriate overuse of the "reference-to" prefix is a sloppy, erroneous practice, and it is based on a misunderstanding of how keywords are supposed to work. If a passport is an important plot point and is spoken about but not actually shown on the screen, "passport" is the preferred keyword. And if someone briefly mentions a passport but it is not an important plot point, then no keyword should be added at all.

In fact, the "reference-to-passport" keyword should not exist at all. My reading of the guidelines, and my longstanding practice, is to only use the "reference-to" prefix for people and certain things (a person, character, title, network, or production company) that does or could have its own non-keyword-related entry on IMDb (e.g. "reference-to-harrison-ford," "reference-to-snow-white," "reference-to-the-matrix," "reference-to-fox-news," and "reference-to-dreamworks"). That is the sole point of the "reference-to" keyword: to avoid confusion in mixing up certain keywords for non-keyword entries on IMDb.  Every other plot point should simply be listed as a keyword without the "reference-to" prefix, whether or not that plot point is literally depicted in the title.

The people who would use "reference-to-a-passport" for your hypothetical scenario are not getting the point. They are also bifurcating keywords for no good reason, thus reducing the usefulness and power of keyword-combination searches. If I want to search for movies where a passport is a plot point, I should be able to do that without worrying about a secondary "reference-to-a-passport" keyword, since there is currently no "or" boolean parameter for keyword searches on IMDb (at least, not that I know of).

I apologize for that tangent, but your example (where something is discussed but never shown on the screen) reminded me of the unfortunate overuse of the "reference-to" prefix; this seems to be happening more and more the past couple of years on IMDb.