The Kantai collection character Saratoga has an overslung launching device. The lower half of this device is modeled after the Thompson Submachine Gun, and for that reason people have started tagging pictures of her that have the launcher with "Thompson submachine gun". I think this is a bad idea for three reasons:
1. It's not actually a Thompson. Only the lower half looks like a Thompson, and some artists do not choose to replicate this, like for example here: https://danbooru.donmai.us/posts/2718284?tags=thompson_submachine_gun where the proportions are drawn so loosely the launcher bears only a minute resemblance to the actual gun
2. Other kantai collection characters with "adapted weapons" are not tagged with the weapon they're adapted from- for example, the Bismarck uses a MG42's rear stock mounted to a gun turret: https://danbooru.donmai.us/posts/1842987?tags=bismarck_%28kantai_collection%29+official_art. this device is not tagged as a MG42, and therefore there's an inconsistency of tags.
3. Tagging it as a "Thompson submachine gun" badly clutters the Thompson tag. I don't think it should be a Thompson for the same reason that kantai collection is no longer tagged as "mecha musume" or "personification"; all the sort-of Thompsons drown out the actual Thompsons. The tag no longer fully helps people find images with actual Thompson submachine guns, now they get mostly kantai collection.