Hello,
My theme and some other themes are in trending position without a sale, meanwhile some others which sell well (published on the same day) are not seen as trending.
Does it mean that there are many people who added cart and thinking about buying?
What’s your experience on this?
I don’t know the exact secret blend of herbs and spices that go into the trending special sauce, but I think it’s a combination of sales, views and comments. Maybe favourites as well, who knows. So you can have a bunch of sales, but with hardly any views and comments, and it won’t be trending… and you can have a bunch of comments and views, but no sales and it might be trending. Maybe the number of people who favourite an item as well, who knows.Or something like that.
Yes, I agree with @SpaceStockFootage, number of comments affects it… Not sure about number of views, but it’s also likely…
May be it’s just view or hits. My few items were trending. Now also one is trending but got sales on that anyway. I think if last three days views count is more than 300, it’s trending. I felt that way with my past items. May be I’m wrong…
Agree with @SpaceStockFootage, 
who knows … then just let it be a mystery. I have notice this ‘problem’ since the first month I joined, there are several items on Print Template > Stationery category which always listed on the first page of trending items list, even with a few or no sales and still there until now.
I checked the list just now, I saw one of the items already has several sales now, less than 10, after at least 4 months there, without any comment, and still there 
. Another item is still has no sales until now after months on the first page … and still trending (1st page) 
I believe there’s someone knows why these items always on the first page of the trending items list … but who knows.
When you get a lot of traffic in your item, the system calculates the Entrances and % Exits in the analytics section. And if you have a lot of those, you got a big chance to get your item Trending without having any sales. Everything counts though. Sales, Comments, Views. When I got the “Trendsetter” badge, I asked around and people told me this. So, I’m not entirely sure of my answer but I hope it helps!
Cheers!