it isn't a (new) symbol per se, but an old symbol and certain letters appearing together. It's like making a "number 1 symbol" tag for "#1", or calling circled 9 "circle 9 symbol".
it's a huge dog whistle. Let me elaborate on what I mean by that. A pre-existing word/token (in this case "queen of spades" in particular, and the spade symbol in general) with an innocuous meaning has been co-opted by some niche (in this case interracial fetishists) who have attached an additional meaning to it, so as to have a convenient "code word". This is how you kill a word, expression or symbol: see "retarded", 卍
Most people will not know the coded meaning and misapply the tag. This is aggravated by the fact that queen_of_spades_symbol now outnumbers queen of spades, and is thus auto-suggested first.
The tag usage appears to be "creeping": case in point, trying to say a spade symbol is isolation is a QoS symbol.
An alarming fraction of posts so tagged are frankly disgusting: racist, misogynistic, or both. Usually when I decide to garden a tag, I include deleted posts, the premise being that on principle deleted posts still should be tagged correctly. Almost immediately I realized that I did not have the stomach for it.
If you want to discuss the usage of a tag, you should rather open a forum topic about it. The usage of a tag won't change after a comment section discussion. @Arcana55
@Arcana55 I always review the artist's previous works to make sure of the individual's artistic disposition before I make context-dependent calls. In the case of this artist, none of his previous Junkos (post #4743324, post #4739964, post #5049289, etc) or other illustrations include the spade tattoo. Given the spread of the Queen of Spades thing from the West to the rest of the world, the fact it was a commissioned work, that tattoo's absence from any other works he has drawn for himself, and the general context, I feel absolutely certain it was an intentional use of that symbol for that context by the commissioner.
Old symbols being co-opted is not a new thing. There are any number of tags on danbooru that were added when their new context became wide enough to be noticed. I don't like the tag either, but my personal feelings have nothing to do with whether or not its usage would be correct in the given context. I simply tag accurately, blacklist what I don't like, and proceed about my business.
That being said, I'm with you on the problem of scope creep. As a related example, I've had arguments with several users who will remain nameless who are convinced that the slightest bit of a tan for a character automatically make the image interracial (examples include explicit artworks of Mirko, an Okinawan Japanese girl from Boku no Hero Academia, and Bea, a tanned Japanese tomboy from Pokemon, being tagged interracial), to say nothing of how every faceless generic male who has a 0.01 more pigment in order contrast to the main girl is now both dark-skinned and interracial. Out of curiosity, I once did a tag check on pixiv and compared it to here. Pixiv had 3,000 pictures tagged as interracial - danbooru has 14,000. To me, that verifies that the fetishists you mentioned have gotten out of control. But gardening that tag is not a problem I'm willing to do more than observe. Tagging on danbooru is something I do to entertain myself when I want to catalog things. I neither wish to get into an overbearing and nauseating debate on the social justice theme of the day nor proselytize Western politics on a Japanese image repository.