This is not a yes or no answer, but a point of discussion.
Harry Potter is one of our largest tags. There's a huge body of questions. These questions can be hard to filter by simple text searches, because searchable terms are often used in questions that aren't about that term.
Want to know more about just Hermione? Good luck narrowing that down. Want to know just about Slytherin? Did you mean Salazar himself or the Hogwarts House? How do you filter out every time a user merely mentions "Slytherin" when they're just talking about a Slytherin, like Draco?
Tagging helps facilitate not just answering the question, but later finding the question and it's answers. Aside from perusing out of personal interest, we have a strong history of citing other answers to strengthen new ones, or to find duplicates.
Our top tags on this site are so large that they and their related tags are often curated by "specialists", people that take an interest in that work and are knowledgeable about it. We have different levels of granularity and grouping in these tags, and should keep that in mind when discussing whether or not to keep a tag. The structure and conventions that work for Lord of the Rings is different than Marvel properties. They're different bodies of work, and we shouldn't try to force a one-size-fits-all tagging policy around them. Story Identification is a whole different beast from Star Trek. We've never really tagged individual Harry Potter films or books, but for Star Wars we have a need to create those individual tags before the movies are even released!
We have the flexibility to make our own tag map, and have our experts help curate and guide new users, write usage guidance, etc.
So, I would encourage people to vote based on:
- Is a Marauder's Map a reasonably helpful tag for people of the Harry Potter Fandom?
- Is it reasonable to assume some people might want to know about just that subject?
- Is the tag unlikely, when used appropriately, to interfere with other Harry Potter tagging (such as the 5 tag limit)?
This seems a more reasonable approach to me than voting on a Harry Potter tag the same way you would for a Game of Thrones tag. Different fandoms have different needs, different things they want to know, and different types of source material.