Cultural appropriation is a topic I come back to regularly. Not all examples of cultural borrowing constitute cultural appropriation. Yet there are some examples of cultural borrowing that are offensive to members of the culture borrowed from.
One lens we can use to think about cultural appropriation is that of boundary maintenance. All groups have a boundary. The boundary may be hard and clear: employment is a group membership that is documented and legally constrained. The boundary may be soft and fuzzy: membership in the Jane Austen fandom requires merely a certain self defined amount of interest in Jane Austen and her works. Most boundaries fall somewhere between.
If a particular element of a culture is part of the boundary maintenance mechanism, then taking on that element as an outsider can be seen as cultural appropriation. Taking on boundary maintaining elements can cause harm. (Note: I am not claiming this is the only type of cultural appropriation.)
It can lead to the incorrect impression that one is a member of a group. Whether or not this is harmful depends on how strictly the group defines its boundaries. Pretending to be part of a reasonably coherent group can harm its reputation . Pretending to like an author will likely just result in confusion. However, it is important to realize that falsely pretending to be a member of a group can be legitimately considered harmful by members of the group.
The second harm is that it can harm the group’s structural integrity by weakening its boundary. This is the sort of harm that comes, for example, from culturally demeaning Halloween costumes. By taking cultural markers of pride and identity and making them frivolous, the group loses access to some of the elements that define them as a group.
The second, in my opinion, is the more harmful aspect of cultural appropriation. When cultural appropriation weakens the sense of connection within a group, then it is harming the ties that create community and strengthen society.
Note that weakening groups via appropriation is a technique activists sometimes use intentionally. For example, gay men hijacked the #ProudBoys hashtag used by a white supremacist group of the same name. Since not all groups create community and strengthen society, it is valid to try to dissolve such groups, and appropriation is a tool in the activist’s toolbox. However, it’s worth acknowledging that such uses are indeed an instance of cultural appropriation.