When I watch 1897, we spend a great deal of time laughing. Quentin is written, appropriately, like and Oscar Wilde character complete with little epigrams that crack me up. Buffy is the same way, especially in the early seasons. If that's what's meant by DS being "funny" I don't have a problem with it.
And I think that's exactly the sort of funny most of us are hoping for. The dialogue during the 1897 period was some of the best of the series. So, if the film's dialogue is anything like that, I for one will be very happy.
And there's also something else to keep in mind: even IF the film does turn out to be a horror comedy, it will be a "dark," "scary," and "bloody" comedy because Depp, Zanuck, and Green have respectively described the script as being those things as well, and we shouldn't lose sight of that.
I just wish I was more familiar with
Beetlejuice because I have no idea what to take from Green's description of the script as a mixture of
Sweeney Todd and
Beetlejuice...